The commands here allow the usage of timer commands. The process of checking whether a timer is over runs every 10 seconds, which means, that a very short timer will not end at its configured time.
Add a new timer.
/timer add <int: duration> <time_format> <string: reason>
Remove a timer. You'll see all your timers reasons, to help you remove the correct timer.
/timer remove <string: timer_reason>
Shows all your timers, when you set them and when they are going to end, along with their reasons.