A simple datapack allowing a player to start, pause and reset a timer.
The timer is shown as a bossbar in the top. This will be added and will never be in the way of another map's features. (Can only affect visibility. The bossbar visibilty can be toggled, for when you don't want to see the timer at all times.)
In short, this datapack is a great addition to every map you wish had a timer.
Addionally a maximum time can be set. When reached, everyone will get a big "Time is up" sign on their screen.
To use this timer, you need access to function commands. For singleplayer maps, you might need to open the game for lan to enable cheats.
To get all the information in-game, just use the command:
/function lion_timer:help