1. Introduction

At first, we will examine in details the events and the dating of what is commonly called Paul's third journey. There are surprises here! If you get disoriented, don't worry, I have a comprehensive recapitulation at the end of this page. Then, we will investigate the composition of the two canonical Paul's epistles to the Corinthians: more surprises. Finally, I invite you to read each one of the letters which includes my own comments. Everything fits!
Note: all dates are C.E. (Christian Era).

2. Dating of the third trip

2.1 Spring of 52:

Gallio was proconsul of Achaia (Ac18:12) from the summer of 51 and for a period of less than one year. The incident reported in Ac18:12-17 (involving Gallio and Paul) is described to have occurred in the latter part of Paul's one year and a half stay in Corinth (Ac18:11). Consequently, it would be in the spring of 52 when Paul went from Corinth to Jerusalem (Gal2:1-10, Ac18:18-22).

Notes:
a) The New Jerusalem Bible chronological table (p. 2071) agrees with that date, as also the NIV Study Bible.
b) Spring was the season to start traveling from a home base (as in Ac20:6, also from Corinth to Jerusalem) and winter the time to stay put:
1Co16:6 "Perhaps I [Paul] will stay with you awhile, or even spend the winter [in Corinth, which he did later, in 57-58 (Ac20:3)] ..."

Furthermore, after his visit to Jerusalem in 52:
Ac18:23 NAB "... then went down to Antioch [as corroborated in Gal2:11]. After staying there some time, he [Paul] left and traveled in orderly sequence through the Galatian country and Phrygia ..."
This kind of travel was most likely to be done during the dry summer/early fall months, therefore pointing to springtime for the start of Paul's trip from Corinth to Judea.
This later travel was done one year and a half after Paul's arrival in Corinth:
"So Paul stayed [in Corinth] for a year and a half, teaching them the word of God." (Ac18:11)
Consequently Paul arrived here in late 50, which is very plausible: that would have given him enough time (from spring to fall) for his "second journey" from Antioch, including another visit to southern Galatia, and setting up new Christian communities in Macedonia & Athens (Ac15:41-17:34).

Period referred to, so far:
[Fall 50 => Spring 52 => Summer 52]
(Green indicates 'new entry')

2.2 Fall of 57:

The most accepted date for the ending of Felix's tenure as procurator of Judea is 60. It is acknowledged that Festus, Felix's successor, lasted in this position only two years. The sudden death (on the job) of Festus was followed by the trial & stoning of James, Jesus' brother (in 62 and reported in Josephus' Antiquities, XX, IX, 1). It happened before the next procurator, Albinus, could arrive. Consequently, the time of Paul's arrest in Jerusalem (Ac21:17-26), around the time of Pentecost (Ac20:16), would be in 58 according to:
Ac24:27 "When two years had passed [after Paul's arrest], Felix was succeeded by Porcius Festus [in late spring 60] ..."
Note: the New Jerusalem Bible chronological table (p. 2071) agrees with that date.

Prior to his arrest in Jerusalem, Paul spent the winter in Corinth:
Ac20:2b-3 "... Now when he had gone over that region [Macedonia] and encouraged them with many words, he came to Greece [Corinth] and stayed three months."
'Romans' was written at the end of this Paul's stay in Corinth:
Ro15:25-26 "Now, however, I am on my way to Jerusalem in the service of the saints there. For Macedonia and Achaia were pleased to make a contribution [see next for money collection] for the poor among the saints in Jerusalem."
And before going to Corinth, Paul spent some time in Macedonia during the money collection for the "Nazarenes". That would be in the fall of 57.

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [Fall 57 => late Spring 58]

2.3 The collection in the fall of 57:

The planning of this collection is well described in the 2Corinthians letter.

Note: the collection for God's people in 1Co16:1-9 refers to another one attempted in 55 during a visit to Corinth the same year, and before the "riot" in Ephesus. This trip is also mentioned in:
Ac19:21-22 "After all of this had happened, Paul decided to go to Jerusalem [to offer the collection to the "Nazarenes"], passing through Macedonia and Achaia.
[which he did, as his second visit, according to 2Co13:2a "I already gave you a warning when I was with you the second time"]
` "After I have been there," he said, "I must visit Rome also". He sent two of his helpers, Timothy and Erastus, to Macedonia while he stayed in the province of Asia a little longer."

In this letter ('2Corinthians'), the collection in Macedonia (fall of 57) was proceeding well:
2Co8:1-4 "Moreover, brethren, we make known to you the grace of God bestowed on the churches of Macedonia: that in a great trial of affliction the abundance of their joy and their deep poverty abounded in the riches of their liberality. For I bear witness that according to their ability, yes, and beyond their ability, they were freely willing, imploring us with much urgency that we would receive the gift and the fellowship of the ministering to the saints."

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [Fall 57 => late Spring 58]
(no change)

2.4 The "riot" in Ephesus:

Ac19:23-34 "And about that time there arose a great commotion about the Way. For a certain man named Demetrius, a silversmith, who made silver shrines of Diana, brought no small profit to the craftsmen. He called them together with the workers of similar occupation, and said: "men, you know that we have our prosperity by this trade. Moreover you see and hear that not only at Ephesus, but throughout almost all Asia, this Paul has persuaded and turned away many people, saying that they are not gods which are made with hands. So not only is this trade of ours in danger of falling into disrepute, but also the temple of the great goddess Diana may be despised and her magnificence destroyed, whom all Asia and the world worship." Now when they heard this, they were full of wrath and cried out, saying, "Great is Diana of the Ephesians!"
So the whole city was filled with confusion, and rushed into the theater with one accord, having seized Gaius and Aristarchus, Macedonians, Paul's travel companions. And when Paul wanted to go in to the people, the disciples would not allow him. Then some of the officials of Asia, who were his friends, sent to him pleading that he would not venture into the theater.
Some therefore cried one thing and some another, for the assembly was confused, and most of them did not know why they had come together. And they drew Alexander out of the multitude, the Jews putting him forward. And Alexander motioned with his hand, and wanted to make his defense to the people. But when they found out that he was a Jew, all with one voice cried out for about two hours, "Great is Diana of the Ephesians!""
The collection happened some time after the "riot" in Ephesus:
Ac20:1 "After the uproar [in Ephesus] had ceased, Paul called the disciples to himself, embraced them, and departed to go to Macedonia [fall of 57]."
But how long did this uproar last?
After the huge commotion, "Luke" wrote (right before Ac20:1, the previous quote):
Ac19:40-41 ""For we are in danger of being called in question for today's uproar, there being no reason which we may give to account for this disorderly gathering." And when he had said these things, he [a city magistrate] dismissed the assembly."
That's it! The impression is given that after the "uproar" and a small speech, the Christians (above all Paul!) are absolved of any wrong doings. And everything is back to normal!

Note: when Paul gets into trouble, the author is quick to point out that it was not his fault (Ac16:19, 18:12-16, 21:27-31, 26:32).

However, in the city magistrate's speech:
Ac19:38-39 "Therefore, if Demetrius and his fellow craftsmen have a case against anyone, the courts are open and there are proconsuls. Let them bring charges against one another. But if you have any other inquiry to make, it shall be determined in the lawful assembly."
And that might have been just what happened, causing Paul and others to go in jail, waiting for a trial.

From one of my esteemed readers, I quote:
"The Roman success in governance of their empire was to leave in place the underlying governing structure, with a provincial governor to oversight the maintenance of order and receipt of the tribute. Consequently the cities were self-governing, with their citizen body and governing council of magistrates, of which the 'Town Clerk' was the senior executive member. Assemblies were held on a regular (monthly, fortnightly) basis, and motions put before them by the council - they were not debative, and the only real means of dissent was negative i.e. vote motions down, but not propose them - hence the chanting which took place on this occasion was their usual means of demanding to be given a vote on a motion to their liking to solve a particular problem.
And of course, as this particular assembly was not summoned by the appropriate Magistrate (Town Clerk) it was an unlawful one. Hence his demand that a proper motion be brought up at a properly constituted assembly and his dismissal of the assembly. And he did not 'absolve the Christians' (I think they were still considered (and considered themselves) a Jewish sect at that stage) - he said that they had not committed sacrilege, which they apparently had not. This left open the possibility of lawsuits between individuals, which is the option he gave to Demetrius et al, and this was entirely normal in the legal system of the day. There were no directors of public prosecution/state attorneys. If a law had been broken, a citizen brought a prosecution before a court.
It seems to me that this is a very likely account - a popular call to meet at a place of assembly; the citizens - most not knowing what was going on - rushing there to find out what the emergency was; being convinced that their prosperity was at stake and chanting for action to fix the problem; a Magistrate, fearful of the consequences from the Roman provincial governor (including a forcible dispersion by troops with casualties, and the magistrates, held responsible by the governor for the maintenance of order, being fined for their failure); and a proposal that a lawful motion be brought before a lawful assembly or complainants bring charges before a proper court.
This passage is one of the ones in Acts which really rings true."

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [Fall 57 => late Spring 58]
(no change)

2.5 The aborted collection in Corinth (spring of 56):

In 2Co1:15-16, Paul wrote:
"And in this confidence I intended to come to you before, that you might have a second benefit; to pass by way of you to Macedonia, to come again from Macedonia to you, and be helped by you on my way to Judea."
The same trip was cancelled:
2Co1:23 "I call God as my witness that it was in order to spare you that I did not return to Corinth."
There, Paul was referring to a trip he "threatened" to do (as in 2Co12:14,13:1-2 written earlier), but did not (2Co1:23,2:1). Instead, he went to Troas (2Co2:12), then to Macedonia to meet with Titus (2Co7:5-7), a "helper", who had been sent to Corinth earlier (2Co12:18). The news from Titus was very good, in regard of the Corinthians accepting Paul again.
And a collection must have started then (56). This is corroborated by what Paul wrote in the fall of 57:
2Co8:10-11 "And here is my advice about what is best for you in this matter: last year you were the first not only to give [the collection in 56] but also to have the desire to do so. Now finish the work, so your eager willingness to do it might be matched by your completion of it, according to your means."
2Co9:1-2b "There is no need to write about this service to the saints [the "Nazarenes"]. For I know your eagerness to help, and I have been boasting about it to the Macedonians, telling them that since last year you in Achaia [Corinth, Athens] were ready to give ..."
2Co8:6 "So we urged Titus, since he had earlier made a beginning, to bring also to completion this act of grace on your part."
What happened? The Corinthians, the year before, in 56, had agreed to begin the collection, started it and then it was interrupted. Why?
2Co1:8-9a gives us a clue:
"For we do not want you to be ignorant, brethren, of our trouble which came to us in Asia: that we were burdened beyond measure, above strength, so that we despaired even of life. Yes, we had the sentence of death in ourselves,"
also 2Co1:10a "He [God] has delivered us from such a deadly peril ..."
Very simply, in the spring the year before, Paul went to Macedonia, got the surprising good news from Titus, decided to come back briefly to Ephesus (as indirectly corroborated in Ac19:29 "... The people seized Gaius and Aristarchus, Paul's travelling companions from Macedonia, ...") and got caught up in the "riot". He got arrested (with other Christians), was sent to prison (or house arrest with others) waiting to stand trial: this disturbing news stopped the collection in Corinth.
Then, more than one year after, he got released: I will demonstrate that next.

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [56 => Fall 57] and [Fall 57 => late Spring 58]

2.6 The prison letters (56-57):

Now, we have to examine the prison letters by Paul to get more information. But which ones are the authentic ones?
Obviously '2Timothy' is a second century creation (as '1Timothy' & 'Titus'); few critical scholars will argue for genuineness on that one. That leave us with 'Philemon' and 'Philippians'. But what about 'Colossians'? Many scholars agree (& I do also) that this letter was written by someone who was close to Paul when he wrote 'Philemon'.

Note: for my argumentation here, it does not matter if Paul or a close acquaintance wrote the letter.
According to Col4:7-9, this letter was allegedly issued with 'Philemon', and sent by the same people, Tychicus and Onesimus the runaway slave. The premise could have been the letter was "forgotten" or "lost" for years. The most important point I'll draw from the letter is that Onesimus and his master, Philemon, were living in Colosse.

Once again, even if it is not needed for the following argumentation, but to avoid confusion, let's say that 'Philippians' is three genuine combined Paul's letters:
'aPhilippians' (written 53-56?, likely 53-54): Php4:10-4:20
'bPhilippians' (written 56-57): Php1:3-3:1a
'cPhilippians' (written 57-58): Php3:1b-4:9
One clue (among others) suggesting these letters were combined is the obvious new introduction of the canonical letter:
Php1:1 "Paul and Timothy, bondservants of Jesus Christ, to all the saints in Christ Jesus who are in Philippi, with the bishops [overseers] and deacons:"
'Bishop(s)' (Greek 'episkopos') do not appear anywhere else in the Pauline genuine letters (Ro,1Co,2Co,Gal,1Th,Phm), including the rest of 'Philippians'. However this word started to be used in Christian texts around 80 (as in '1Clement').

We will be interested in the second (and the longest) one: the prison letter.

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [56 => Fall 57] and [Fall 57 => late Spring 58]
(no change)

2.7 Paul's prison term in Ephesus:

In the prison letters, there are plenty of evidence that Paul languished "in chains" in Ephesus and not in Rome.

2.7.1 In chains (or bonds --Greek root 'desmon') (plural):
Paul was definitively in bounds as a prisoner:
Php1:13b "... and to all the rest, that my chains are in Christ;"
Php1:14 "... having become confident by my chains ..."
Php1:16 "The former preach Christ from selfish ambition, not sincerely, supposing to add affliction to my chains;"
Also in:
Col4:3 "... for which I am also in chains, ..."
Col4:18 "... Paul. Remember my chains ..."
and finally in:
Phil1:9-10 "... being such a one as Paul, the aged, and now also a prisoner ... while in my chains,"
Phil1:13 "... that on your behalf he might minister to me in my chains for the gospel."
However "Luke" did not describe Paul in Rome in the same way:
Ac28:16 "Now when we came to Rome, the centurion delivered the prisoners to the captain of the guard; but Paul was permitted to dwell by himself with the soldier who guarded him."
Ac28:20 "... I am bound with this chain [notice the singular! This is also a different word (Greek root 'halusis')]."
Ac28:30 "Then Paul dwelt two whole years in his own rented house, and received all who came to him,"

Evidently "Luke" did not depict Paul's captivity in Rome as the one ("in chains") in 'Philippians'. Why? Maybe because the author knew it was two different ones. And "Luke" probably had access to 'Philippians' (as explained here).
Please note "Luke" used 'desmon' regarding Paul in Jerusalem & Cesarea (Ac20:23, 22:30, 23:39, 26:29 & 26:31) but made a distinction (with 'halusis') when Paul is in Rome.

Note: it seems that "Luke", as a Roman citizen and proud of it, intended to show that Paul (the author's hero) founded the Christian Church in Rome (Ac28:17-31), as the apotheosis of his apostolic work. Furthermore, "Luke" is prone to have the Romans (especially centurions) be considerate for Paul and often acting as his protector (Ac13:7,16:35,39,19:31,37,22:26-29,23:10,23-24,27:43,28:7) for obvious reasons (see also Lk7:5 "Because he [a centurion] loves our nation and has built our synagogue").
Consequently, the author gave some very decent accommodation to Paul and elevated him to an almost deified patriarch status, who could summon the leaders of the Jews of Rome (Ac28:17) and create Christianity from the top. Of course, through Paul's own letter to the Romans, we know there was a thriving Christian community in Rome, well before Paul had a chance to go there (it is acknowledged that "Luke", in view of conflicts with 'Acts', did not know about 'Romans', and also '1&2Corinthians' & 'Galatians').
And why "Luke" did not say what happened after the two years in Rome?
Here are two plausible explanations:
a) The elders of the Philippian Christians might have known about Paul's execution in 63-64. But the 1Clement letter (written in 80-81, according to my dating), read all over Christianity:
"I have evidence that in many churches this epistle was read aloud to the assembled worshippers in early days" (Eusebius, 'The History of The Church', 3, 16)
mentioned that Paul "having come to the extremity of the West" [in Ro15:24,28 Paul planned to go to Spain] and having borne witness before rulers, he departed at length out of the world [seemingly not from Rome!] ..." (ch.5)
An open ending is non commital and avoids disputes.
b) "Luke" added up more details about the siege & destruction of Jerusalem (picked up from Josephus' Wars, published 78!). That was bound to bring some doubt about the dating of GLuke. By not covering Paul's death, the logical conclusion of 'Acts', the impression is given that 'Acts', and consequently also the gospel, were written before Paul's end (and therefore prior to 70!).

2.7.2 The palace guard:
Php 1:12-13 "But I want you to know, brethren, that the things which happened to me have actually turned out for the furtherance of the gospel, so that it has become evident to the whole palace guard, and to all the rest, that my chains are in Christ;"
Could Paul have said that of the huge imperial palace guard in Rome?
Certainly not: thousand of soldiers & their officers were part of this guard and would not have known a Jewish sect leader who never was a public person here. However, in Ephesus, this guard was very small. And with Paul being a public preacher here for more than two years (Ac19:9-10,20:31), it is a lot more plausible Paul was then in Ephesus.

Note: any capital city of a Roman province (as Ephesus) was allotted a small contingent of an imperial palace guard.

2.7.3 Travel plans:
Col4:10 "Aristarchus my fellow prisoner greets you, with Mark the cousin of Barnabas (about whom you received instructions: if he comes to you, welcome him),"
How to explain Mark would go through an inland Asia minor city as part of a trip from Rome? That's very unlikely. However Colosse was three days walk away from Ephesus and on the way to some likely destinations such as southern Galatia, Antioch and Jerusalem.
Also, there is no mention of length, cost or danger for the trips planned by Paul's friends either to Philippi (Php2:19,25 --only 200 miles by boat from Ephesus) or to Colosse (Col4:8-9, Phil1:12), especially after Paul's atrocious trip to Rome taking months (Ac27:1-28:16)?
Evidently, the origin of these planned trips could not have been Rome.

2.7.4 Fellow prisoners:
Aristarchus was arrested in Ephesus:
Ac19:29 "So the whole city was filled with confusion, ..., having seized Gaius and Aristarchus, Macedonians, Paul's travel companions"
So it should not be surprising to find him as a prisoner here with Paul: Phil1:24 and
Col14:10a "Aristarchus my fellow prisoner greets you, ..."
But years later, according to Ac27:2 "So, entering a ship of Adramyttium, we put to sea, meaning to sail along the coasts of Asia. Aristarchus, a Macedonian of Thessalonica, was with us [on the way to Rome]."
Aristarchus was then a free man, and very unlikely to become a prisoner with Paul when in Rome.

Epaphras, also a prisoner with Paul,
Phil1:23a "Epaphras, my fellow prisoner ..."
Col4:12a "Epaphras, who is one of you ..."
appears to be an inhabitant of Colosse (and probably the true author of 'Colossians', according to Col1:7-8,4:12-13) and the likely founder of the Christian community there. Then why would he surface in Rome?
However, because Ephesus was the Christian center of Asia Minor, he could have been arrested here during one of his visits (Colosse being three days walk away from Ephesus).

And, in the genuine prison letters, there is no mention of the Roman residents named in Ro16:3-16, either as prisoners or visitors.

2.7.5 Onesimus (Phil1:1-25):
How to explain a runaway slave could have traveled by land and sea, across unfamiliar territory, for about one thousand miles (and without getting caught and killed)?
However, going to Ephesus, a few days walk from his master's home in Colosse, was very possible.

2.7.6 Paul's refuge:
The following was probably a polite social statement:
Phil1:22 "But, meanwhile, also prepare a guest room for me, for I trust that through your prayers I shall be granted to you."
Here, Paul alluded to a place of rest after his hoped for release. But how could he write that to a friend more than one thousand miles away?
Certainly, there were Christians in Italy (Ac28:14-15) where Paul could have find comfort without going through a long & tiring trip.
But if Paul was a prisoner in Ephesus, then Colosse & Philemon's house, far enough from his enemies, but within easy reach, could have been an appropriate place of refuge.

Note: why did "Luke" never write about Paul's jailing in Ephesus?
Possibly not to show Paul prone to be arrested (as "... a trouble maker, stirring up riots ..." Ac24:5) and put in chains.
As already mentioned, "Luke" has Paul's days in Rome rather comfortable and the two years in the Cesarea jail (58-60) were the same:
Ac24:23 "So he [Felix, the procurator, a man of bad reputation] commanded the centurion to keep Paul and to let him have liberty, and told him not to forbid any of his friends to provide for or visit him."
The length of (& reason for) the imprisonment there is explained by:
"Meanwhile he [Felix] also hoped that money would be given him by Paul, that he might release him. Therefore he sent for him more often and conversed with him. But after two years Porcius Festus succeeded Felix; and Felix, wanting to do the Jews a favor, left Paul bound." (Ac24:26-27)

But how to explain Paul was in chains in Ephesus whereas "some of the officials of Asia, who were his friends" were there (Ac19:31a)? Why bother to write anything about it in 'Acts'? Even if "Luke" intended to demonstrate the "riot" was not Paul's fault, nothing would be gained about reiterating he was incarcerated there.
And then, how to deal with the fact that Paul was in chains as (allegedly) a Roman citizen?
Ac16:37-38 "[in Philippi, 50] They beat us publicly without a trial , even though we are Roman citizens, and threw us into prison. ... they heard that Paul and Silas were Roman citizens, they were alarmed."
Ac22:29b "[in Jerusalem, 58] and the commander was also afraid after he found out that he was a Roman, and because he had bound him."
So the blank between Ac19:41 & Ac20:1
And then "Luke" could not be expected to relate all the tribulations of Paul. Actually, few have been narrrated in 'Acts', considering:
2Co6:4-5a "Rather, as servants of God we [Paul and companions] commend ourselves in every way: in great endurance; in troubles, hardships and distresses; in beatings, imprisonments and riots; ..."
2Co11:23b-25a "I [Paul] have worked much harder, been in prison more frequently, been flogged more severely, and been exposed to death again and again. Five times I received from the Jews the forty lashes minus one. Three times I was beaten with rods, once I was stoned, ..."

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [56 => Fall 57] and [Fall 57 => late Spring 58]
(no change)

2.8 The remaining years:
If Paul was imprisoned in 56, how can we account for the four years from the spring of 52, the time of Paul's trip to Jerusalem?
According to:
Ac20:31 "Therefore watch, and remember that for three years I did not cease to warn everyone night and day with tears."
Paul preached as a free man in Ephesus for a grand total of three years.
Now, let's assume (that will fall into place later) that Paul arrived in the winter of 52-53 in Ephesus (starting this trip from Jerusalem in the spring of 52, as already established). Then:
Ac19:8 "And he went into the synagogue and spoke boldly for three months, reasoning and persuading concerning the things of the kingdom of God."
Then after that:
Ac19:9b-10 "he departed from them and withdrew the disciples, reasoning daily in the school of Tyrannus. And this continued for two years, so that all who dwelt in Asia heard the word of the Lord Jesus, both Jews and Greeks."
That's a total of two years and three months, bringing us to the spring of 55 when the following was planned:
1Co16:5-8 "After I go through Macedonia, I will come to you [in Corinth] - for I will be going through Macedonia.. Perhaps I will stay with you for awhile, or even spend the winter , so you can help me on my journey, wherever I go. I do not want to see you now and make you a passing visit; I hope to spend some time with you, if the Lord permits. But I will stay on at Ephesus until Pentecost."
The same trip is rather obscurely mentioned in:
Ac19:21-22 "After all of this had happened, Paul decided to go to Jerusalem, passing through Macedonia and Achaia.
[which he did, as his second visit, according to 2Co13:2a "I already gave you a warning when I was with you the second time". Time elapsed: let's say about three months]
` "After I have been there," he said, "I must visit Rome also". He sent two of his helpers, Timothy and Erastus, to Macedonia while he stayed in the province of Asia a little longer.
[about nine months (as a free man): from summer of 55 to spring of 56. I'll come back to that later]"
The obscurity can be explained: the trip, regarding the Corinthians, was a failure; Paul was rejected and had to wait to start all over again:
2Co7:2-3 "Open your hearts to us. We have wronged no one, we have corrupted no one, we have cheated no one. I do not say this to condemn; for I have said before that you are in our hearts, to die together and to live together."
2Co13:1-2 "This will be my third visit to you. ... I already gave you a warning when I was with you the second time. I now repeat it while absent: on my return I will not spare those who have sinned earlier or any of the others;"
Let's account for the three preaching years of Paul in Ephesus (Ac20:31):
Two years and three months from winter of 52-53 to spring of 55. Then we add nine months from the summer of 55 when Paul returned from his unsuccessful trip to Macedonia & Corinth (about three months duration). That brings us to the spring of 56 and Paul short trip to Troas, Macedonia & back to Ephesus right before the "riot". We have a total of three years (give or take a few months).

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [early 53? => Spring 55] and [Spring 55 => Summer 55] and [Summer 55 => Spring 56] and [56 => Fall 57] and [Fall 57 => late Spring 58]

2.9 Late arrival in Ephesus in 53:

But how to explain the late arrival in Ephesus by Paul in the winter of 52-53?
Paul had the intention to go back to Ephesus after his visit to Jerusalem in the spring of 52:
Ac18:19-21 "And he came to Ephesus, and left them there; but he himself entered the synagogue and reasoned with the Jews. When they asked him to stay a longer time with them, he did not consent, but took leave of them, saying, "I must by all means keep this coming feast in Jerusalem;
[probably Pentecost as for the next trip to Jerusalem (Ac20:16)]
` but I will return again to you, God willing." And he sailed from Ephesus."
As we saw already, Paul spent some time in Antioch on the way back. Then he went overland through Galatia toward Ephesus:
Ac18:22b-23 NAB "... then went down to Antioch [as corroborated in Gal2:11]. After staying there some time, he [Paul] left and traveled in orderly sequence through the Galatian country and Phrygia, bringing strength to all the disciples."
But Paul must have tried to be in Ephesus before winter. However it is probably at that time that Paul got stranded in some Galatian town because he was ill. Certainly that would explain his late arrival. "Luke" hinted to a delay:
Ac19:1 "And it happened, while Apollos was at Corinth, that Paul, having passed through the upper regions, came to Ephesus."
The sickness is mentioned in the Galatians letter because, despite his illness, Paul managed to start a Christian communities there among the Gentiles:
Gal4:13-15 "You know that because of physical infirmity I preached the gospel to you at the first. And my trial which was in my flesh you did not despise or reject, but you received me as an angel of God, even as Christ Jesus. What then was the blessing you enjoyed? For I bear you witness that, if possible, you would have plucked out your own eyes and given them to me."
and, for the first time in 'Acts', disciples are said to exist in these parts (Ac18:23b, already quoted).

Note: Paul did two trips before to "southern Galatia", one with Barnabas (Ac13:2-14:27) and the other one (in 50) with Silas (Ac15:40-41) and Timothy (Ac16:1-4) on his way to Macedonia. There is no mention of delays in those trips and both were rather hectic. It is also unlikely that Paul's companions would have left him alone stranded with strangers. But according to 'Galatians', Paul was traveling on his own when he got ill: no companion is named or mentioned, the same goes for 'Acts' (18:23,19:1), referring to the same trip ( more details & map here).
This delay would explain a late arrival in Ephesus, sometime in the middle of the winter of 52-53.
So now, all the time and years are accounted for.

Periods referred to, so far:
[Fall 50 => Spring 52 => Summer 52] and [Fall 52 => early 53] and [early 53? => Spring 55] and [Spring 55 => Summer 55] and [Summer 55 => Spring 56] and [56 => Fall 57] and [Fall 57 => late Spring 58]

2.10 Recapitulation:

a) Spring 52: Paul's trip to Jerusalem from Corinth (fourteen years (Gal2:1) after the one in 38). The "council" of Jerusalem takes place then (See Appendix B for explanations).
b) Summer and early fall 52 (or earlier): Paul spends time in Antioch (dispute with Peter: Gal2:11-14) and departs (alone).
c) Fall 52 to winter 53: Paul becomes sick on his way to Ephesus and recuperates in "northern" Galatia where he makes converts (Gal4:13-15; Ac18:23,19:1a).
d) Winter 53: Paul's arrival in Ephesus. He learns Apollos & Peter had visited Corinth and each one got followers at his detriment (1Co1-4).
e) Winter 53 to spring 55: Paul preaches in Ephesus for two years and three months (Ac19:8,10). He feels partially abandoned by the Corinthians (1Co9). But, later, the situation improves greatly.
f) Spring 55: Paul's trip to Macedonia and then Corinth (2nd one here: 1Co16:5-8; 2Co13:1-2), where Paul is rejected. Likely no collection (as planned in 1Co16:1-4) is done.
g) Summer 55 to spring 56: Paul stays in Ephesus (about nine months).
h) Spring 56: Paul's short trip to Troas and Macedonia (where Paul hears the good news from Titus) then back to Ephesus (2Co1:15-24,7:5-7). Meanwhile a collection is started in Corinth (2Co8:10b-11).
i) Late spring 56: The "riot" in Ephesus.
j) Late spring 56 to fall 57: Paul is imprisoned in Ephesus. The collection in Corinth is aborted (2Co8:10b-11).
k) Fall 57: Paul is freed and goes to Macedonia (probably Philippi first).
l) Fall 57 to early spring 58: Paul visits the Macedonian Christians and then stays in Corinth (for three months (Ac20:3a); the third trip to that city). The collection is restarted and completed in Corinth (Ro15:26).
m) Late spring 58: Paul's arrival in Jerusalem and arrest (Ro15:25-26,31; Ac20,21)

Notes:
A) The NIV Study Bible (introduction to 'Romans') does not account for any prison term in Ephesus. But it stipulates that 'Romans' was written in the early spring of 57. That was before Paul's trip to Jerusalem and after a collection in Macedonia and Achaia (I agree with this context), during a three months winter stay in Corinth (Ac20:3). Consequently, a dating of 56 for the "riot" in Ephesus would be implied.
B) The NIV Study Bible is also in agreement for the start of the third missionary journey of Paul (in Ephesus) in early 53. Then, the three years of Paul's preaching in Ephesus mentioned in Ac20:31 would bring us to 56 and the "riot".

3. The Corinthians letters

3.1 The 1Corinthians letter is a combination of three letters by Paul:
'1aCorinthians' (written early 53): 1:10-4:21
'1bCorinthians' (written later in 53): 9:1-27
'1cCorinthians' (written early 55): the rest (except 1:4-9,14:33b-35,15:3-11,15:23-28 added later. See included explanations)

Why is '1Corinthians' made up of three different letters?
a) Different travel plans:
'1aCorinthians' --> 1Co4:17-19 "... but I will come to you very soon ..."; "... I am sending to you Timothy, ..."
'1cCorinthians' --> 1Co16:5-11 "After I go through Macedonia , I will come to you ... But I will stay on at Ephesus until Pentecost, ..." ; "... if Timothy comes, ..."

b) Different relationship between Paul and the Christians of Corinth:
Paul is partly rejected in '1aCorinthians':
1Co1:11b-12 "... there are quarrels among you. What I mean is this: One of you says, "I follow Paul"; another, "I follow Apollos"; another, "I follow Cephas"; still another, "I follow Christ.""
and also in '1bCorinthians':
1Co9:1b-2a "... Am I not an apostle? Have I not seen Jesus our Lord? Are you not the result of my work in the Lord? Even though I may not be an apostle to others, surely I am to you! ..."
However, he appears fully accepted in '1cCorinthians':
1Co16:10-11b "If Timothy comes, see to it that he has nothing to fear while he is with you, for he is carrying on the work of the Lord, just as I am. No one, then, should refuse to accept him ..."
totally in control, very confident, feeling free to ramble & reveal his inner thoughts and dealing as a bishop would towards his flock. For example, Paul is judging a sinner (as God would!):
1Co5:3b-5a "... And I have already passed judgment on the one who did this, just as if I were present. When you are assembled in the name of our Lord Jesus and I am with you in spirit , and the power of our Lord Jesus is present, hand this man over to Satan ..."
and putting himself as equal of the "Lord" in issuing commands:
1Co7:10,12 "To the married I give this command (not I, but the Lord): A wife must not separate from her husband. ... To the rest I say this (I, not the Lord): If any brother has a wife who is not a believer and she is willing to live with him, he must not divorce her."

c) Insertion:
'1bCorinthians' (all about Paul's problems) is evidently an insertion in a passage where Paul is rambling about Christian food, idolatry and sexual immorality (1Co5:1-8:13,10:1-11:1).
1Co8:11-13,10:1-3 "And because of your knowledge shall the weak brother perish, for whom Christ died? But when you thus sin against the brethren, and wound their weak conscience, you sin against Christ. Therefore, if food makes my brother stumble, I will never again eat meat, lest I make my brother stumble. [1bCorinthians inserted here]
Moreover, brethren, I do not want you to be unaware that all our fathers were under the cloud, all passed through the sea, all were baptized into Moses in the cloud and in the sea, all ate the same spiritual food,"

3.2 The 2Corinthians letter is also a combination of three letters by Paul:
'2aCorinthians' (written late 55): 2:14-7:4 (except 5:10,6:14-7:1 added later. See included explanations)
'2bCorinthians' (written early 56): 10:1-13:10
'2cCorinthians' (written late 57): the rest (except 1:1-2,13:11-14 added later)

Why is '2Corinthians' made up of three different letters?
a) Insertion:
'2aCorinthians' is obviously an insertion in a passage dealing with Paul going to Macedonia to meet Titus.
2Co2:12-13,7:5-6 "Now when I went to Troas to preach the gospel of Christ and found that the Lord had opened a door for me, I still had no peace of mind, because I did not find my brother Titus there. So I said good-by to them and went on to Macedonia. [2aCorinthians inserted here] For when we came into Macedonia, this body of ours had no rest, but we were harassed at every turn--conflicts on the outside, fears within. But God, who comforts the downcast, comforted us by the coming of Titus, and not only by his coming but also by the comfort you had given him."

Note: '2aCorinthians' was written from the point of view of Paul and his helpers, using "we", "us" & "ours". The Christian "editor" likely changed the "I", "me" & "mine" in the three verses after the insertion. Afterwards, things become more normal:
2Co7:7-8 "... us ... me ... me ... my ... I ... my ... I ... I ... I ... my ..."

b) Different relationship between Paul and the Christians of Corinth:
Almost fully rejected in '2aCorinthians':
2Co6:12-13 "We have spoken freely to you, Corinthians, and opened wide our hearts to you. We are not withholding our affection from you, but you are withholding yours from us. As a fair exchange --I speak as to my children-- open wide your hearts also."
2Co7:2-3 "Make room for us in your hearts. We have wronged no one, we have corrupted no one, we have exploited no one. I do not say this to condemn you; I have said before that you have such a place in our hearts that we would live or die with you."
and also in '2bCorinthians':
2Co12:20b-21a "... I fear that there may be quarreling, jealousy, outbursts of anger, factions, slander, gossip, arrogance and disorder. I am afraid that when I come again my God will humble me before you ..."
2Co13:1-3a "This will be my third visit to you. "Every matter must be established by the testimony of two or three witnesses." I already gave you a warning when I was with you the second time. I now repeat it while absent: On my return I will not spare those who sinned earlier or any of the others, since you are demanding proof that Christ is speaking through me."
But Paul is fully accepted (but cautious) in '2cCorinthians':
2Co1:21-22 "Now it is God who makes both us and you stand firm in Christ. He anointed us, set his seal of ownership on us, and put his Spirit in our hearts as a deposit, guaranteeing what is to come."
2Co7:7 "... He [Titus] told us about your longing for me, your deep sorrow, your ardent concern for me, so that my joy was greater than ever."
To the same Christians, Paul is imploring for reconciliation in '2aCorinthians' (2Co5:19-20), he is most angry in '2bCorinthians' (2Co11:13-15) but very forgiving (2Co2:5-11,7:8-9) & friendly in '2cCorinthians':
2Co7:16 "I am glad I can have complete confidence in you [the Christians of Corinth]."

c) The mentioned other letter:
In '2cCorinthians', Paul keeps referring to a letter he wrote earlier:
2Co2:3-4a "I wrote as I did so that when I came I should not be distressed by those who ought to make me rejoice ... For I wrote you out of great distress and anguish of heart and with many tears ..."
2Co2:9 "The reason I wrote you was to see if you would stand the test and be obedient in everything."
2Co7:8 "Even if I caused you sorrow by my letter, I do not regret it. Though I did regret it -- I see that my letter hurt you, but only for a little while--"
The letter in question is undoubtebly '2bCorinthians':
2Co12:21 "I am afraid that when I come again ... I will be grieved over many who have sinned earlier ..."
2Co13:5-6 "Examine yourselves to see whether you are in the faith; test yourselves. Do you not realize that Christ Jesus is in you-- unless, of course, you fail the test? And I trust that you will discover that we have not failed the test."

3.3 When were the genuine Pauline epistles written, relative to Paul's third journey?

Notes:
a) '1Thessalonians' (not shown here) was written earlier, during the second journey, after Paul arrived in Corinth for the first time (late 50 to early 51) (references: 1Th1:1,2:2,17,3:1-2,6; Ac17:1,16,18:1,5). In this epistle, there are suggestions of raptures to heaven (4:16-17) and of the Sacrifice (5:9-10).
b) 'Romans' was written towards the end of the third journey, after the completion of the collection in Macedonia and Achaia, when Paul was still in Corinth (for a three months stay) and before going to Jerusalem (references: Ro1:7,15,15-26,31,16:1-2,23; 1Co1:14; Ac20:1-3). Several interpolations have been proposed for 'Romans': Ro16:25-27 is the most accepted.
c) Common themes, features and details are indicated (in Italics) for 'Hebrews' and subsequent Pauline epistles. Please consult HJ-3b for the relative dating of 'Hebrews' and Paul's letters to the Corinthians.

Here is a recapitulation, according to my studies, as explained in HJ-3b, HJ-3b extension, Appendix B, this page, and the aforementioned (nine) ones about each Corinthians & Philippians letter:

a) Spring 52: Paul's trip to Jerusalem from Corinth (fourteen years after the one in 38). The "council" of Jerusalem takes place then.
b) Summer and early fall 52 (or earlier): Paul spends time in Antioch (dispute with Peter) and departs (alone).
c) Fall 52 to winter 53: Paul becomes sick on his way to Ephesus and recuperates in "northern" Galatia where he makes converts.
d) Winter 53: Paul's arrival in Ephesus. He learns Apollos & Peter had visited Corinth and each one got followers at his detriment.
'1aCorinthians' written spring 53
e) Winter 53 to spring 55: Paul preaches in Ephesus for two years and three months. He feels partially abandoned by the Corinthians.
'1bCorinthians' written later in 53
'aPhilippians' written from early 53 to early 56?, likely 53-54
{'Hebrews' written (by Apollos) in 54} (pre-existence (explained) (1:1-3a,5-10,2:5-8), "new covenant" (explained) (8:8-13,9:1-20), Sacrifice (explained) (1:3,5:8-9,7:27,9:11-15,10:1-14), (Jesus') blood (9:12,10:19,29), co-Creator of the universe (explained) (1:2,10), Moses' followers dying in the wilderness (3:16-17), home in heaven for Christians (12:22-23), atonement for sins (explained) (1:3,2:17,10:12), "Son of God" (explained) (1:5,8-9), Christians as seed and heirs of Abraham through the "promise" (2:16,6:13-17), the heavenly Jerusalem (12:22-23), "at the right hand of God" (explained) (1:3,13,8:1,10:12,12:2))
But, later, the situation improves greatly.
'1cCorinthians' written early spring 55 (First (for Paul): pre-existence (8:6,10:3), "new covenant" (11:25), Sacrifice (clear-cut) (5:7), (Jesus') blood (10:16,11:25,27), co-Creator of the universe (8:6), Moses' followers dying in the wilderness (10:2-8))
f) Spring 55: Paul's trip to Macedonia and then Corinth (2nd one here), where Paul is rejected. Likely, no collection (as planned in 1Co16:1-4) is done.
g) Summer 55 to spring 56: Paul stays in Ephesus (about nine months).
'2aCorinthians' written summer 55 (First (for Paul): home in heaven for Christians (5:19,21), atonement for sins (5:19,21))
'2bCorinthians' written early spring 56
h) Spring 56: Paul's short trip to Troas and Macedonia (where Paul hears the good news from Titus) then back to Ephesus. Meanwhile a collection is started in Corinth.
i) Late spring 56: The "riot" in Ephesus.
j) Late spring 56 to fall 57: Paul is imprisoned in Ephesus. The collection in Corinth is aborted.
'Philemon' and 'bPhilippians' written then
k) Fall 57: Paul is freed and goes to Macedonia (probably Philippi first).
l) Fall 57 to early spring 58: Paul visits the Macedonian Christians and then stays in Corinth (for three months; the third trip to that city). The collection is restarted and completed in Corinth.
'2cCorinthians' written fall 57 (First (for Paul): "Son of God" (1:3,19))
'Galatians' (First (for Paul): Christians as seed and heirs of Abraham through the "promise" (3:16-29), the heavenly Jerusalem (4:26))
'cPhilippians'
& 'Romans' written winter 58 (First (for Paul): "at the right hand of God" (8:34))
m) Late spring 58: Paul's arrival in Jerusalem and arrest

Notes:
a) For details on '1Thessalonians' and 'Hebrews' (including dating), see 'HJ-3b'
b) For details on '1Thessalonians' (interpolations), 'Hebrews' (interpolations), 'Galatians' (including dating), and 'Romans', see 'HJ-3b extension'
c) Translation of '1Thessalonians'
d) Translation of 'Hebrews'
e) Translation of 'Philemon'
f) Translation of 'Galatians' (2:7-8, except "but to the contrary," is an interpolation as explained on this page)
d) Translation of 'Romans'