I see the new Horizons add on is available from "Holiday 2015" - when is that in English?
I went on holiday last week - does that count?
What holiday was it last week?
This is one colloquialism that never made sense to me. A holiday, or holy day, has been expanded to cover a day given off by government mandate or employer election. A vacation is a day you choose to take off and vacate your workplace.
The holiday season refers to the period of time at the end of the year during which people celebrate various holidays, generally around Christmas. I'm not really a big fan of that phrase covering over a month of time though.