i dont know. mine had always been ok.

lol. what did u do with your calendar? any new input you've put it or any settings you changed?

i would greenify it and control the wakelock further with amplify at 3600 or 7200

but before that, try clearing the calendar's app cache. see if that would help.

looks to me, the calendar is trying to fetch some data or generate an alarm, but ran into some error and that made it keep going into a loop.

try clearing cache for both calendar and calendar storage apps. cache only. dont clear storage.
then restart the phone. make sure its has a stable internet connection. wifi would be good. then open the calendar app. let it run for a while. then see if it is still causing high wakelocks.

lol sorry sorry
btw, can u guide him on step to undo the mikey effects