[Flask] strftime 포맷 형식

directive	예시	비고
%a	Sun, Mon, …, Sat
%A	Sunday, Monday, …, Saturday (en_US);
%y	00, 01, …, 99	year 2자리
%Y	2013, 2014, …, 9998, 9999	year 4자리
%m	01, 02, …, 12 month
%b	Jan, Feb, …, Dec
%B	January, February, …, December
%d	01, 02, …, 31	day
%H	00, 01, …, 23	Hour 24
%I	01, 02, …, 12	Hour 12
%p	AM, PM
%M	00, 01, …, 59	minute
%S	00, 01, …, 59	second