Javascript date - setting UTC month

Question

Today i ran my automates tests and wondered why I got an error about some date specific stuff.

Turns out that setting a fixed UTC month is not working anymore. But yesterday it did. There are no changes I am aware of.

I tried running the following code

var d = new Date();
d.setUTCMonth(1);
d.toISOString();

which returns

"2019-03-01T10:28:42.108Z"

But month should obviously be february. Also why is the day set to 01 and not today (29)

Tested on Chrome, Edge, Firefox.

Any advice? Am I doing something wrong? Is there a bug in the library?

`var newdate = d.setUTCMonth(1); console.log(newdate.toISOString());` — GrafiCode, Mar 29 '19 at 10:36
dates "auto correct" in javascript ... clearly there is no 29th feb 2019, so 1 mar 2019 is correct ... try date.setDate(date.getDate() + 365) for any date, you'll add (3 in 4 times, damn yuo leap years) exactly a year .. — Jaromanda X, Mar 29 '19 at 11:15
It will also happen on the 31st of any moth that follows a 30 day month. ;-) — RobG, Mar 29 '19 at 13:46

score 1 · Answer 1 · answered Mar 29 '19 at 10:37

1

hum... funny error.

Try this :

var d = new Date('2019-03-10T00:00:00');
d.setUTCMonth(1);
d.toISOString();

It's because today is end of month and you're initializing the date to today.

answered Mar 29 '19 at 10:37

Francisco

1

today is march 29. I live in germany so even when the timezone is different, march has 31 days. – user3740359 Mar 29 '19 at 10:39
1

but you set to 29 of February that doesn't exist – Francisco Mar 29 '19 at 10:40
`today is end of month` it's 28th or 29th Mar around the world ... nowhere is today the end of the month :p – Jaromanda X Mar 29 '19 at 11:17

score 0 · Answer 2 · answered Mar 29 '19 at 10:49

0

Kindly try this:

var d = new Date('2019-03-10T00:00:00');
d.setUTCMonth(1); 
console.log(d.toISOString());

answered Mar 29 '19 at 10:49

Saket Yadav

that works. returns 2019-02-09T23:00:00.000Z. @Francisco found the problem with the non-existent Feb 29 – user3740359 Mar 29 '19 at 11:06
A good answer should explain why the OP has their issue and how your code fixes it. – RobG Mar 29 '19 at 13:48

2 Answers2