Someone on the forum was asking how to reset the day counter in the F3 screen. To do that, you do World#setFullTime() with a long value indicating number of ticks the world has been up.

I figured I'd throw this together is said person was asking for a plugin solution and not a code solution.

To use, type /worldtime then the time value. To reset to the start, pass 0. Do not pass a "human" time like 4:00PM or "5 weeks". It wants number of ticks. So like /worldtime 300000 = day 12 for example.

You can optionally (well, not optionally if ran at console) pass a target world after the time. If you are a player in the game, it will default to the world you are in if you do not pass a world name.

Permission required is worldtime.set