How can one skip holidays in nurture/engagement programs?

If you simply want to stop all casts for two weeks over the holidays, use the program Setup tab and switch the program Off, then back On later. That is the recommended efficient control for Engagement Programs during a holiday season.

If you want a custom schedule for all local holidays, then you need to build and use a suppression list for all programs, but the programs would need to rerun again in the future to send to those that were suppressed during the holiday. There is no built-in blackout feature for sending emails.

Hi ​@Adam Bencan, 

If you're planning ahead, you can set up a batch campaign that targets members of the engagement program who haven't been exhausted and are still in the flow, then pause them for X days and resume them after X days. This can be scheduled in advance for future dates.

That said, if you're comfortable manually toggling the program on and off around the right dates, what ​@BlaneMcMichen-1 suggested is simpler and works just as well.