Subtract x days from a String Date - React

Question

Suppose I've got a date in string format, such as "2021-07-19". How can I subtract x days from this date that is represented as a string?

I have tried to convert the string into a date first, then subtract the number of days, and convert back to a string, but that doesn't work.

const dateString = "2021-07-19"
const previousDayDate = new Date(dateString)
previousDayDate.setDate(previousDayDate.getDate() - 1)
const previousDayDateString = previousDayDate.toString()

The ultimate result should be "2021-07-18". Instead, I get the date as a full string: Sun Jul 18 2021 01:00:00 GMT+0100 (British Summer Time)

use moment.js. `npm i moment` and usage: `moment(youDate).diff('days', 'otherDate')`; — Najam Us Saqib, Jul 19 '21 at 14:28
Is there a way to do this without using `moment`? As far as I know, there are warnings when using `moment` as it will soon become deprecated (or certain parts of it I believe). — Adam, Jul 19 '21 at 14:28
https://date-fns.org/ has helpful methods to help with date manipulation. — Chris Farmer, Jul 19 '21 at 14:30
@NajamUsSaqib thanks but my requirement is still not to use `moment` — Adam, Jul 19 '21 at 14:31
@ChrisFarmer thank you. My method almost works but I just need to find a way to get it into the format I'd like rather than a full string. — Adam, Jul 19 '21 at 14:32
Related: https://stackoverflow.com/questions/3552461/how-to-format-a-javascript-date — Spencer Wieczorek, Jul 19 '21 at 14:34
@RoboRobok you're absolutely correct. Thank you for pointing that out. — Adam, Jul 19 '21 at 14:41
The issue is the original parse is UTC but all other methods are local, hence the time is offset by the local timezone offset. — RobG, Jul 20 '21 at 05:59

score 1 · Answer 1 · answered Jul 20 '21 at 05:58

The reason you get the wrong date is that "2021-07-19" is parsed by built–in parsers as UTC, but all the other methods you're using are local, so you appear to get the wrong date or time. Other than that, your algorithm is sound. Just parse the string as local to being with:

// Parse string in YYYY-MM-DD format as local
function parseISOLocal(s) {
  let [Y, M, D] = s.split(/\W/);
  return new Date(Y, M-1, D);
}


console.log(parseISOLocal('2021-07-20').toString());

This is a very common issue.

Kinglish · Accepted Answer · 2021-07-19T14:51:06.693

0

Note, the snippet below didn't work in my locale until I changed the input date to YYYY-MM-DD.

// const dateString = "2021-19-07" - your format
const dateString = "2021-07-19" // format testable in my locale
const previousDayDate = new Date(dateString)
previousDayDate.setDate(previousDayDate.getDate() - 1)
const previousDayDateString = `${previousDayDate.getFullYear()}-${('0' + (previousDayDate.getMonth()+1)).slice(-2)}-${('0' + previousDayDate.getDate()).slice(-2)}`;
console.log(previousDayDateString)

edited Jul 19 '21 at 14:51

answered Jul 19 '21 at 14:44

Kinglish

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Thanks for your answer. However, I can see the snippet showing the result subtracting 1 month instead of 1 day. In any case, I've done something almost identical in my answer below. – Adam Jul 19 '21 at 14:46
1

thanks, forgot those were zero-based. Answer updated – Kinglish Jul 19 '21 at 14:48
Thanks. However, it still shows as the same date (2021-07-19) – Adam Jul 19 '21 at 14:49
Ok. apologies. I accidentally treated the getDate as if it was zero-based, which it isn't. That is fixed. Oddly It gives me the console.log of 2021-07-17 now - but not you? – Kinglish Jul 19 '21 at 14:52
It gives me "2021-07-18" which is I think what we want (1 day subtracted from 2021-07-19) – Adam Jul 19 '21 at 14:55
Right - that is interesting because it gives me 2021-07-17. Different locales... – Kinglish Jul 19 '21 at 14:57

Adam · Answer 3 · 2021-07-19T18:09:08.727

0

Thank you all for the suggestions. I followed the same convention as Spencer's comment above (How to format a JavaScript date?) by doing:

const dateString = "2021-07-19"
const previousDayDate = new Date(dateString)
previousDayDate.setDate(previousDayDate.getDate() - 1)

const previousDayString = previousDayDate.toLocaleDateString("en-CA").split(",")[0]

console.log(previousDayString)

edited Jul 19 '21 at 18:09

answered Jul 19 '21 at 14:44

Adam

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score 0 · Answer 4 · answered Jul 19 '21 at 14:48

0

Using Moment.js

const dateString = moment("2021-07-19", "YYYY-MM-DD").startOf("day")
const previousDayDateString = dateString.subtract(1, "days").format("YYYY-MM-DD");

answered Jul 19 '21 at 14:48

Sirajeddine Aissa

26
3

OP explicitly stated they are not using moment nor is this tagged – Spencer Wieczorek Jul 19 '21 at 15:49

Subtract x days from a String Date - React

4 Answers4