I kinda explained it on my post above yours. Each mode can be played on 2 different days (they are dated) and for each mode you have to play 2 hours max to unlock a tier. Players are allowed to split the playtime between both days. When the day arrives with another mode to play you start again to play 2h on the specific mode in total. More hours for the same double day won't be rewarded
So if I play 2hrs of siege today, I don’t have to play it again tomorrow?