Christmas 2017 OR Jan 1st 2018
date(2017,12,25) || date(2018,1,1)
Jan 1st OR DEC 25
((day()=1)&(month()=1)) || ((day()=25)&(month()=12)) ||
Labor Day - 1st Monday of May
(day<=7)&(month()=5&(weekday()=2)