Join GitHub today
GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.Sign up
YYYY should be yyyy and DD should be dd #520
The tokens accepted by date-fns are different with what most languages and libraries support.
I focus here on YYYY and DD.
They all follow the specifications from the Unicode Consortium CLDR: http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Format_Patterns
Interpreted languages are mostly based on C function
Edit: somewhat related to #351