Happy birthday for boxing day. Just don't expect any birthday. My sister and nephew are both boxing day and it seems the card shops think nobody has birthdays in December.
I agree with Boo, also when you tipped the tradesman. That is why Boxing Day cannot fall on a Sunday. This year Monday should officially be Boxing Day but people seem to ignore that now. The 26th is officially St Stephen's day as well.
In olden times there used to be a poor box into which better off people would put gifts. The day after Christmas the box was opened and contents distributed to the poor of the parish. Hence Boxing Day.