I'm not exactly sure what you're trying to do with ROTA. Have a field in the the table that indicates if the day is part of the on or off, based on the 4 day on and 4 day off cycle? For example, Jan 1-4 should have a value of On, while Jan 5 - 8 should be Off, and then have this repeat?
If so, try the following:
AddColumns(CalendarList,"OnOff",If(Mod(DateDiff(Date(2023,01,01),DateField),8)<4,"On","Off"))
If the on/off cycle doesn't start on 1/1, then of course adjust that date. If the calendar isn't just for the current year, that date can be from any year. It gets the number of days between the specified date and today, and uses MOD to do division and get the remainder, which effectively gets a number from 0 to 7 for each date. A value of < 4 is set to "On", 4-7 is set to "Off".
Or, perhaps I interpreted your question incorrectly.