I have fond memories of an iClassic staff member having a 9/11 holiday. I warned him, he did it anyway, **** got out of hand and I had to do major damage control.
Keep holidays to commercialised international events (i.e. celebrated by multiple countries).
- Christmas
- Easter
- Valentines Day
- New Years Eve
- Halloween
You may argue that Christmas/Easter is religious but it's commercialised to hell so it doesn't matter so much.
I am fiercely opposed to celebrating National holidays/events (4th July, Canada Day etc.) because do one, you need to celebrate every single god damn holiday ever because players will bitch.