In version 3.6.0, format() shifts day backwards with string input, e.g. format('2024-04-03', 'yyyy-MM-dd') shift day to "2024-04-02"

[weihe8892]

In version 3.6.0, day shift when format with string as input, e.g. format('2024-04-03', 'yyyy-MM-dd') output as 2024-04-02

[sumodmatto]

@weihe8892

I was unable to reproduce the issue you mentioned in my environment. The following code returns "2024-04-03" as expected:

import { format } from 'date-fns';

// Formatting a string date directly
const dateString = "2024-04-03";
const formattedDateString = format(dateString, "yyyy-MM-dd");
console.log(formattedDateString); // Outputs "2024-04-03"

// Creating a Date object and formatting it
const dateObject = new Date(2024, 3, 3); // Note: JavaScript months are 0-based
const formattedDateObject = format(dateObject, "yyyy-MM-dd");
console.log(formattedDateObject); // Outputs "2024-04-03"

Could you please provide more detailed information about the problem?

[fturmel]

If you pass a string to the format function, it will use the native Date constructor internally. You can easily encounter this pitfall when dealing with JS dates:

When the time zone offset is absent, date-only forms are interpreted as a UTC time and date-time forms are interpreted as local time.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date#date_time_string_format

This means that if you are in a time zone with a negative offset, you are constructing a date time that is the day before what you intended in local time. And since date-fns uses local time by default, the format function will output the day before.

---

If you need to parse a date-only string and treat it as local, the easiest ways would be to append "T00:00:00" to it, or to use the parseISO function before passing it to format. As @sumodmatto mentioned, creating the date with numerical inputs is also a common alternative: new Date(2024, 3, 3)

You can also make date-fns v3 operate in UTC by using the UTCDate companion package if that's what was intended.