While many studies try to evalutate the impact of MMO on real life, the reverse effect mostly remain unwatched.

While many producer offer ingame content related to seasons or holidays, there is also other side-effect of real-life cycles.

About the special event related to real-life, producers have to be careful with their pick. Religion / curtural clash can occurs. Easter can't be called easter since a group of people wouldn't like it, same for christmas other religious holidays.

Taking that asside, the real life cycle impact on MMO. I can see 3 big annual thing.

September -> stutent return in class. Some students will start to play like hell, while some student will almost stop playing do concentrate on their study.

Mai/June -> reverse effect, some student start to play like hell, other stop playing to due having more real life activity like full time job, party...

Summertime: While less intense activity occur (many big guild will drop or slow down activity), number of player remain similar... but play on more varied playtime. More people during the day, cause evening hardcore player to beleive less people play the game..

Thus said, don't neglect your real life... it'll last longer than any game :).

Enjoy!