The JavaScript Date Constructor

I came across a little gotcha with the Date constructor recently. The new Date() constructor takes a unix timestamp or a dateString, which according to mozilla should allow a version of ISO8601.

Here’s the issue

If my timezone is Easter Standard Time (US east coast) and I create a new date without a time zone.

Something like:

new Date('2019-01-29');

My browser actually assumes the date is in UTC timezone and returns.

Mon Jan 28 2019 19:00:00 GMT-0500 (Eastern Standard Time)

Possible Solutions

Appending a time to the date string will force the browser to parse it the local time zone of the browser.

new Date('2019-01-29' + 'T00:00:00');

or if you are using moment js, you can pass your date string directly to moment.


Both solutions correctly return

Tue Jan 29 2019 00:00:00 GMT-0500 (Eastern Standard Time)