영어 -st, -nd, -rd 와 -th 쓰임새

The correct one is 12th of February.

 

Tricky it may seem but here is the rule:
When a number ends with 1, 2, or 3, the number must be suffixed with “st”, “nd” or “rd” respectively. However, if the number before 1, 2 or 3 is 1, then it must be suffixed with “th.”

 

This might help:
1st, 2nd, 3rd, 4th, 5th,
6th, 7th, 8th, 9th, 10th,
11th, 12th, 13th, 14th, 15th,
16th, 17th, 18th, 19th, 20th,
21st, 22nd, 23rd, 24th, 25th,
31st, 42nd, 53rd, 61st, 72nd,
73rd, 101st, 102nd, 103rd, 104th,
111th, 112th, 113th, 121st, 131st,
132nd, 133rd, 210th, 211th, 212th,
222nd, 1000th, 1001st, 1011th, 1021st