Damn close to wasting monthly challenge

Can anyone tell me when, for sure, the XP Cap resets? I’m only one win away from the monthly challenge when the XP Limit was reached, and if I go to play, and it hasn’t reset yet, I’ll be really pissed to lose that XP. I’m in the eastern time zone, and I’m posting this at 12:01am, Sunday. Normally I wouldn’t start a whole thread for one question, but sometimes my cap has reset at noon, and sometimes at 5am, so I really have no idea how this system works.

PS. XP Cap is -Yoink- to begin with.

when the daily challenges reset i think the cap resets, so check how much time is left on those