Although I still wasn't sure what "singles day" is (some sort of reverse of Valentine's Day?), it's a little clearer by itself than "double sticks day" (a phrase which yields all of 3 results on Google).
Googling "singles day" explained everything.
Googling "singles day" explained everything.
The 1st-Jan is considered to be small singles day, then "11th-Jan" and "1st-Nov" the middle singles day, and "11th-Nov" the ultimate singles day.