Sure, your suggestion would work for most days of the
month.
But what about the last day of the month or the last day of the year?
You add 1 and you get 30th of february or 32nd of december. =)
Lots of {{#if}} statements? There may be a better way... A
{{UNIXTIME}} variable giving seconds since the epoch would be very
useful... I'm surprised there isn't one already, but it shouldn't be
difficult to add.