Date strings with fractions of a second marked as invalid when formatting

[PontusMagnusson]

I'm trying move away from using moment.js and as I'm trying to format some dates that are in my system, date-fns tells me that the dates are of an invalid format.

I have a function that I use to format dates which looks as follows:

import { format } from "date-fns";

export function formatDateTime(date) {
  if (date) return format(date, "yyyy-MM-dd HH:mm:ss");
}

When trying to format this date string 2021-08-09T10:52:37.6532978 it throws an error and tells me the date is invalid, but moment.js handles it just fine.

It handles 2021-05-07T14:54:53 perfectly fine, so I assume it has something to do with the second fractions at the end.

If I use utcToZonedTime from date-fns-tz on the failing string first, it manages to understand the date string.

Is there something I'm missing? Thanks.

Edit:

import { format } from "date-fns";

export function formatDateTime(date) {
  if (date) return format(new Date(date), "yyyy-MM-dd HH:mm:ss");
}

Creating a new Date object seems to work, but I'm not sure why just passing the string throws an error.

[fturmel]

format only accepts a Date instance or a number (ms since Unix epoch) as its first argument. If you start with a string representation of a date, you need to parse it into a Date object first (with the parse or parseISO functions for example).
https://date-fns.org/v2.23.0/docs/format

Careful using strings in the Date constructor, it is discouraged by MDN because the implementation varies with each runtime.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/Date

[PontusMagnusson]

Ah, thank you. I've misunderstood the documentation a bit. That the function sometimes accepts strings also confused me.

[fturmel]

format should not work with a date string in date-fns v2 for any scenarios, it will throw a RangeError.

In v1 however, format did accept and parse strings internally. This is one of the major changes between the two versions.
https://date-fns.org/v2.23.0/docs/Upgrade-Guide#string-arguments

So, maybe you referenced v1 docs or examples at some point? Or maybe you've been using v1 all along? If you have examples of v2 format working with a string date I'd love to see it.

[PontusMagnusson]

Yeah that was a mistake on my part. I noticed that some of the strings got parsed in another component, so the docs are of course correct.

Thanks for the help :)

[fturmel]

You're welcome, and thanks for confirming!