parse date-fns returns one day previous value

Question

I am trying to parse date using date-fns library for the first time (I removed moment.js and I will introduce date-fns in my project) but, when I use parse function, I get one day previous as result. I read in this topic

parse function in date-fns returns one day previous value

that problem is due to timezones but I could not be able to fix my problem because I receive dates in the format "yyyyMMdd". This is my code

var start ="20210119"; var stop ="20210130"; const dateFrom = parse(start, "yyyyMMdd", new Date()); console.log("date form",dateFrom);

Output of my console log is: 2021-01-18T23:00:00.000Z

It's unclear what you want. Do you want to parse yyyyMMdd format timestamps as UTC? By default, if no timezone is specified, timestamps will be parsed as local, which is why you see a difference between the initial timestamp and generated timestamp—the original is parsed as local but logged as UTC. — RobG
– RobG, Commented Sep 13, 2021 at 10:20
Probably a duplicate of Proper way to parse a date as UTC using date-fns. — RobG
– RobG, Commented Sep 13, 2021 at 10:28

Terry Lennox · Accepted Answer · 2021-09-13 10:31:18Z

Your dateFrom date is actually correct, assuming you want it in your local time.

The reason it's showing an hour earlier in your console output is because it is being displayed in UTC time (hence the 'Z' for Zulu at the end). I assume your local time is one hour ahead of UTC in January.

We can use Date.toLocaleString() to output the time in either UTC or local time.

If we output in local time, we see the date is actually correct (2021-01-19 00:00:00), and if we output in UTC (set the timeZone to 'UTC') we see it is one hour earlier (as in your console output).

We can also output the local date using Date.getFullYear(), Date.getMonth() and Date.getDate().

var start ="20210119"; var stop ="20210130"; const dateFrom = dateFns.parse(start, "yyyyMMdd", new Date()); console.log("Date from (is Date object):", dateFrom instanceof Date); console.log("\nDate from (console.log):",dateFrom); console.log("Date from (UTC):", dateFrom.toLocaleString([], { timeZone: 'UTC' })); console.log("\nDate from (Local):", dateFrom.toLocaleString()); console.log("Date from (Local):", dateFrom.toDateString()); console.log("Date from (Local):", `${dateFrom.getFullYear()}-${dateFrom.getMonth()+1}-${dateFrom.getDate()}`);

<script src="https://cdnjs.cloudflare.com/ajax/libs/date-fns/1.28.5/date_fns.min.js"></script>

ok, thanks for your answer but I will obtain a date and not a string?
Yes, absolutely. dateFrom is always a Date object, we're just converting to string to show in the console.

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