let a = new Date()
a.setDate(1) <--- this set date to the first date of this month.
However
let b = new Date ('2020-02-15')
b.setDate(1)
b.toISOString() -> returns'2020-02-02T00:00:00.000Z'
What's going on?
Timezones. The difference comes from the fact that you're initializing date a with the current time, and b at midnight local time, which (depending on the time of day where you are) can be a different day when represented in UTC. setDate() sets the "day" part of the Date object based on your locale.
let a = new Date()
a.setDate(1);
let b = new Date('2022-02-14');
b.setDate(1);
console.log("UTC:")
console.log(a.toISOString());
console.log(b.toISOString());
console.log('Local timezone:')
console.log(a.toLocaleString())
console.log(b.toLocaleString())The above code will stop proving its point in about a month, so for the benefit of People Of The Future™ here is the current output:
UTC:
2022-02-01T17:11:37.114Z
2022-02-02T00:00:00.000Z
Local timezone:
2/1/2022, 12:11:37 PM
2/1/2022, 7:00:00 PM
I think it have something to do with your TimeZone and Time Settings
date.toISOString() always displays the date as
YYYY-MM-DDTHH:mm:ss.sssZ
Where Z means UTC+0 TimeZone
try adding the the time and the TimeZone when constructing the date
something like
let date = new Date('2020-02-12T00:00:00.000+02:00');