When [RELEASE] Sabbath/Holiday Mode Scheduler activates the Mode "Shabbat" A 25 hour period during which many lights and devices go on and off based on time. Some are easy because they are triggered by the Shabbat Mode beginning, At the start of Shabbat Mode many lights come on. But during Shabbat based on how long it has been from the start of Shabbat some lights or devices turn off. Then the next Morning with Shabbat Mode continuing lights come on and lights go off based on absolute time or time relative to Shabbat. Some times Shabbat mode can continue for 3 days.
All of my lights that are on relative timers I have set up to be relative to that day's sunset or sunrise time. I haven't found the need for a timer based on a relative offset from when Shabbat started. Most of my timed lights use absolute time.
You can look at the documentation for the "holidayDay" attribute on this page:
You can use that to set up different timers for different days of a long holiday.
Otherwise, it sounds like you are asking about how to set up a timer that's only active during a particular mode, and you'll be able to find people to help you with that in the forum for whatever app you're using to create the timers.
