It’s burried in all that documentation we don’t have.
You have to manually set vacation, it’s at the top of your settings page. We don’t auto-vacation people on timeouts.
You can still make moves on vacation, and it will add time in the case of Fischer time, as well as decrement the Canadian byo-yomi turn counter appropriately.
Weekends begin on Saturday at 00:00:00 UTC and end on Sunday 23:59:59 UTC (plus or minus a few seconds for processing ;))
Vacation accrues at 1/8th speed (so, every 8 days you get one day of vacation) and is capped out at 30 days. New players begin with 20 days available.