From Longman Dictionary of Contemporary Englishbe on daysbe on daysJOB/WORKto work during the day at a job you sometimes have to do at night I’m on days this week. → day
Examples from the Corpus
be on days• I'm on days this week.• It worked till Thursday, but then Amy was on days off and Joe had a cold.• But it was on days like these that one longed for a friend, hoped for a caller.• It was on days like these that the emptiness came back and one grew desperate.• When you were on days, you had a bunch of forms. 