Here's a nice fork with npm integration and no memory-leaking cache: https://github.com/QwantResearch/strftime
This is a JS version of PHP's strftime(string [,date] [,locale])
d = new Date(); console.log(strftime("%Y/%m/%d %H:%M", d));
It's inspired by this API: https://github.com/samsonjs/strftime
Thanks to important optimizations, this version of strftime is up to 5 times faster than samsonjs' version for a single call,
and it's up to 70 times faster for repeated calls.
Here's the speed test comparing the two functions: http://jsperf.com/strftime-closure
Here's my test page (results appear in the console): http://xem.github.io/strftime
Note: the timezones are not implemented yet.