Date .format behind by one day

[cdt-eth]

I have "startDate": "2021-11-01" & "endDate": "2022-11-01" and need them converted to MM/dd/yyyy, which I did (below), but it's showing the day before. I'm assuming it's some timezone issue, but how do I fix this or think about it? I'm in the USA and EST. Best way to account for this?

const start = format(new Date(startDate), 'MM/dd/yyyy');
const end = format(new Date(endDate), 'MM/dd/yyyy');

console.log(start);
console.log(end);

// 10/31/2021 but should be 11/01/2021
// 10/31/2022 but should be 11/01/2022

[fturmel]

Yeah, date-fns works with local time zones only at the moment. The problem is you're passing strings in the JS Date constructor which treats the input as UTC, but the date-fns functions work on local time zone representations of the date.

[...] date-only strings (e.g. "1970-01-01") are treated as UTC, not local
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/Date#parameters

import { format, parseISO } from "date-fns";

console.log(format(parseISO("2021-11-01"), "MM/dd/yyyy")); // 11/01/2021
console.log(format(new Date(2021, 10, 1), "MM/dd/yyyy"));  // 11/01/2021

[fturmel]

Also, if you're running this server-side in Node, another approach could be to set the environment's time zone to UTC explicitly with process.env.TZ='UTC'

[cdt-eth]

oh wow, perfect. Yeah parseISO is what I needed thank you!