Prefix any of the day tokens with the letter "s" (s for start), to have these tokens appear only on the first of the month.
On other days the token converts to a blank. Note that this is not a zap token; blank means no text.
On Thursday, June 1st:
•[sd] = 1
•[sDDD] = THU
•[sDddd] = Thursday
On May 3rd, [sd], [sDdd], [sDddd] are all blank.