Hello foxahead, i've been using your mod for a while now never had a problem with it, just tried to launch it on 1.7.10 and it seem to crash for some reason is there a way for me to send in a crash report?
here's what it says when i launch it
he game crashed whilst there was a severe problem during mod loading that has caused the game to fail
Error: cpw.mods.fml.common.LoaderException: java.lang.ClassNotFoundException: foxahead.simpleworldtimer.SimpleWorldTimer

AFTER THE UPTADE IT WORKS FLAWLESSLY THANK YOU!

I just tested on MultiMC.

1. Added new instance 1.7.10
2. Installed latest stable Forge 10.13.4.1614
3. Downloaded SumpleWorldTimer mod for 1.17.10
   SimpleWorldTimer-1.7.10-1.1.2.jar
   https://www.curseforge.com/minecraft/mc-mods/simple-world-timer/files/2859158
4. Put it in the mods folder of the created MultiMC instance.
5. Run. And it starts without issues.

Maybe you are using wrong mod version? For Minecraft 1.17.10 you should use SimpleWorldTimer-1.7.10-1.1.2.jar.
Maybe you have some outdated Forge version? I recommend latest stable Forge 10.13.4.1614.