[BFA - 8.3.7x11] Can't create guild events on calender

Hey, for some reason I can't create guild events on the calendar.

When I'm trying to create a guild event first it opens the event tab and a message pops up saying "Enter a valid time" and right after that when I'm trying to change anything in that tab (desc or name) it writes "Enter a valid time"

Right then when I'm trying to create it, it sends me this message "Internal Calendar Error".
https://imgur.com/a/mvRbNNv

PS: i created that topic here just now realized i did it on the wrong section https://forum.wowcircle.com/showthread.php?t=1144974

Will inform our devs.