[O] Holidays without fixed dates

[Pete Ley]

For instance, New Year's Day is always on January 1st, but something
like the start of Daylight Saving Time is always around the same time
but on the closest Sunday.

Is there a ready-made solution for working this sort of thing into the
agenda? So far I just have holidays in my agenda that have fixed dates
with ++1y repeat intervals on them. I'm just wondering if there exists a
solution or if I should make one. 

Thanks,
Pete