You want the first of every month before the 2nd of any month???
You could a helper column filled with formulas:
=text(c1,"ddmmyyyy")
and drag down
and sort by that.
If you have a list of (say) birthdays and want to group them by day of the month
(disregarding year), you could use a formula like:
=text(c1,"mmddyyyy")
and drag down
and sort by that.