Datejs - A JavaScript Date Library

Found out about this nifty date package for JavaScript today: Datejs. Its chainable interface makes the code read very naturally:

// What date is next thursday?;
// Add 3 days to Today;
// Is today Friday?;

It also does quite a bit of natural English parsing, like Date.parse(‘next thursday’), although most date libraries support that too. I think the chainable interface stands out here as something special. Let's contrast that with some perl code to calculate yesterday, shall we??

my @lt = localtime(time - 86400);
return ($lt[5]+1900) .'-' . ($lt[4]+1) . '-' . ($lt[3]);

(Disclaimer: I didn't actually write that, but it's in a legacy app I sometimes maintain. I'm sure there is a cleaner way in perl to write that code, I just wouldn't know it, nor do I care to!)