JavaScript Date: Why are these two dates different?

Question

Here is the code from my debugger:

new Date('05-20-2015').toString()
"Wed May 20 2015 00:00:00 GMT-0500 (Central Daylight Time)"
new Date('2015-05-20').toString()
"Tue May 19 2015 19:00:00 GMT-0500 (Central Daylight Time)"

I expected the same results, but why are they different?

Answer 1

The ISO format (ex YYYY-MM-DD is a short form) will be considered as the UTC time zone.

Other date strings will be treated as the local time zone.

MDN Source

Related

• Why does Date.parse give incorrect results?

Manually set the time zone

var d1 = new Date('05-20-2015'); // local timezone

var d2 = new Date('2015-05-20'); // UTC timezone
d2.setUTCMinutes(d2.getTimezoneOffset()); // need to set to local timezone

console.log(d1.toString() === d2.toString()); // true

Run codeHide result

Answer 2

I think the difference is in how the value is evaluated.

new Date('05-20-2015').toString();//parse the date using local time zone
new Date('2015-05-20').toString();//parses date as if it is in GMT

As you can see, there is a difference of 5 hours between the setpoints

Date.parse ()

, , parse() . RFC2822/IETF (RFC2822, 3.3), . ", 25 1995 13:30:00 GMT". , , , ", 25 1995 13:30:00 +0430" (4 , 30 ). ISO, ES5, UTC. UTC . RFC2822 3.3 ( ES5 ISO 8601), .

2015-05-20 ISO8601, UTC.

, , new Date('2015-05-20 GMT-0500')