JavaScript Date time different once deployed to Heroku-CodePudding

Locally, everything is accurate by the minute. Once deployed to Heroku, the difference between the times are off by about 6 hours. I am not looking to convert Heroku time zone (would like it to remain UTC). I've tried everything from getTimezoneOffset() conversions to different date formats and I still end up with the same result. How can I have these 2 date times match each other and not be offset by hours when deployed? Why are they different, when formatted the exact same way?

// Used to calculate current date time

const currentDate = new Date();
// ^ Production - (2021-10-12T19:12:41.081Z)
const time = `${currentDate.getHours()}:${currentDate.getMinutes()}`;
const fullDate = `${currentDate.getMonth()}/${currentDate.getDate()}/${currentDate.getFullYear()}`;
const currentDateFormatted = new Date(`${fullDate} ${time}`);
// ^ Production - (2021-10-12T19:12:00.000Z)

const currentParsedDateToUTC = Date.parse(currentDateFormatted.toUTCString());

// Used to calculate an event date time

const eventDate = new Date(`${event.date} ${event.endTime}`); // same exact format as above
// ^ Production - (2021-10-12T13:12:00.000Z)
const eventParsedDateToUTC = Date.parse(eventDate.toUTCString());

const isExpired = (currentParsedDateToUTC > eventParsedDateToUTC); // works locally, but not in production

In this example, the event date and start time is identical to the current date time. How can I prevent them from being vastly different?

CodePudding user response：

That is because the Heroku server is in a different timezone than yours, you can handle it by converting the time format from your frontend, I recommend you use moment.js for example in your frontend you can convert like this:

npm install moment --save

And then you can create a function just to change the format to display:

const formatDatetime = (
  datetime = "N/A",
  format = 'LLL' // here is your format
) => {
  return moment(datetime).isValid()
    ? moment(datetime).format(format)
    : datetime;
};

CodePudding user response：

So -- Heroku is returning the correct UTC local time, as of this writing it is 2021-10-12T19:36:00.000Z.

You're asking Heroku to interpret 2012-10-12 13:12 as a date, but you're not specifying what timezone it should use, so it defaults to its own local time of UTC.

Everything here is working as expected.

What you I think are implicitly asking is that you want it to interpret 13:12 as being in your local time. However, Heroku has no way of knowing what your local time is, so you'll need to track the timezone of events in your database.

The only reason this is working locally is because your local server happens to be in the same timezone as you -- if I were to connect to your local server from my timezone, I'd experience the same problem.