Javascript日期表现不同

Question

I am executing the following in chrome developers console,

var d = new Date("2010-03-20"); d
Fri Mar 19 2010 17:00:00 GMT-0700 (PDT)
var d = new Date("2010/03/20"); d
Sat Mar 20 2010 00:00:00 GMT-0700 (PDT)
var d = new Date("2010-3-20"); d
Sat Mar 20 2010 00:00:00 GMT-0700 (PDT)
var d = new Date("2010.3.20"); d
Sat Mar 20 2010 00:00:00 GMT-0700 (PDT)
var d = new Date("2010.03.20"); d
Sat Mar 20 2010 00:00:00 GMT-0700 (PDT)

My question is why is it behaving differently for "2010-03-20" where it is giving Mar 19 ?

If I do getUTCDate(), I am getting 20, but why is it different only for 2010-03-20. Is it an active bug in javascript date ?

Answer 1

It's not a bug, it's awkward but intended

The quick answer is that new Date("2010-03-20") is interpreted as a ISO-8601 date that, by default, is expressed in UTC (no timezone).

Any other date string that don't fit the YYYY-mm-dd format ('.' instead of '-', '3' instead of '03') is read with the current client timezone information.

And on top of that Date.prototype.toString() prints the date-time based on the client timezone.