Cryslo Time is a simple mod designed to log the amount of time a player spends in the server, the data is stored in an SQLight database and MySQL is planned for a future release.
Commands /ctime - Shows the current total time in the server and the date/time you first joined. /ctime [player] - Shows the total time of another player and the first join date/time (OP only).
Installation Place the JAR file in your plugins folder and restart your server, you should then be able to use the /ctime command.