So is the extra day, or two days during a leap year, simply appended to the year, waited out and ignored?

It's an interesting concept; similar to the Time-slip in Red Mars. Wanting a Martian day to equal that of an Earth day, colonists define the time between 00:00 and 00:01 as being 39 minutes 40 seconds in length.

I guess most peoples' minds go immediately to, "do I have to work it?". Mine did.