Define Days Off for Gantt Chart

Hello,

I found the option to highlith days off in Gantt Chart. Two questions:

1. Is it possible to elapse the duration of the same amount of days off? i.e. I have two week-end "sunk" in my bar --> I want the bar to be 4 days longer.
2. Is it possible to define a custom list of Days Off? By default only Saturday and Sunday are days off, is possible to enrich the list with bank holidays, summer shutdowns, etc ?

Thanks!