How to see when players was on server lat time

This may be a bit "crude", yet it helps. Just place this anywhere in the world and you can do a process of elimination.

Example: Guestbook

There should also be a main log file you can go to in the server directory to check out who was online and such. It's even dated to the current date, past ones, and such so it shouldn't be that hard to find.

You could try using my Plugin in combination with a Discord-WebHook

[Server Admin Plugin] Discord Plugin v0.12.0

You can configure it to just display login/logout.

Alternatively you can open the world database with an SQL editor. In the "Player" table, there is a column "LastTimeOnline" which contains the last time a particular player was online as a milliseconds timestamp. To turn it into a date (+time), just copy the timestamp, remove the last three digits (to turn it into a seconds timestamp / unix timestamp) and enter it on this homepage, for example: https://www.unixtimestamp.com/index.php

If you want to know when the last player was online, you could sort the table (by this column) in descending order and just check the timestamp of the first entry.