According to the Description tab at CourseForge we read:

"With Forge, there is a keybind (normally unbound) to access the config. Go to Options/Controls, assign a key to the WorldTime config, press that key ingame. Once you're done configuring, you can delete the keybind.

But when I go to Options/Controls there is no section for the WorldTime mode to set a keybind. Therefore there is no way to bring the configuration window for the mod ingame or otherwise.

I went to the config folder directly and could only find a .json file with a lot of variables.

If the configuration keybinding is not fixed at least add comments or labels to the variables to identify the variables in order to help make the changes directly in the .json file.