I was rank 1 Fire mage (Mythic Coven) on Feb 20th, but the next day i lost my historical 100% rank - Why is this? That seems a bit unfair 
Kalstrom
https://www.warcraftlogs.com/rankings/17#boss=2073&class=Mage&spec=Fire
That is just how the rankings work. When someone does better than you they are put over you.
No you keep the 100% historical log, but i think you have to hold the log for 12 hours or more?
Historical rank is not about âI had rank 1 for 5 minutes.â Remember that at EU peak there are like 8000 reports in the queue processing, some of which may have happened before your parse, some after, etc.
Some people live log, some people upload 4 hours later after their raid is over.
For all of these reasons, historical ranks are updated in 24 hour windows, which guarantees both that the dayâs logs are processed and that everyone who wants to upload for that day has done so.
I have recently made a UI change to make it more clear when you have a number that is not âlocked inâ yet. Youâll now see the number in italics with a * next to it in your character profile pages. As long as that number looks like that, itâs not finalized yet, and somebody could come along and beat you once their report gets processed.
Well I had rank 1 for at least 12 hours from the date on the log, not 5 mins, so basically Ive been screwed over by the system (24 hours needed to keep your 100% historical log), which I completely agree with the system btw, otherwise, people left, right and center will get 100 percentile historic logs saved all over at the start of new tiers when logs are constantly being broken. But this far into a tier, its fair to say, I think being beat on a mythic boss within 12 hours is very rare and just unlucky. Considering I have raid on the tuesday, I guess the day before reset is just a bad time to be scoring for logs⌠=[
Thanks for your reply and time anyway 
thanks for explaining as you were not the only one who couldnât understand whatâs going on with this. thanks alot.