take Monday 9off)

It is not required, but it is not forbidden either. The sentence becomes more formal if you (1) use "rest day" instead of "day off", and (2) omit the word "off" where you have shown it in parentheses. However, I don't think "in lieu" is the right phrase to use. We say that a day off on a normal working day, given to someone because they have worked on one of their rest days, is "in lieu" of that rest day.

A working day off awarded because Christmas falls on Saturday is an extra break, and is not in lieu (in place) of anything.

Thanks, Contrex.

I agree with your comments.

Christmas falls on Saturday so we are entitled to take Monday off as the holiday.


"Which is our day off" would probably only be used if someone works a schedule that isn't Monday through Friday.

How about . . .

Since Christmas falls on Saturday this year, Monday will be considered the holiday vacation day.

Thanks Sullyfish and Parados.