Change ISO Date String to Date Object - JavaScript

Question

I am stuck in a weird situation and unfortunately,even after doing some RnD and googling, i am unable to solve this problem.

I have a date string in ISO format, lik

Answer 1

I also did not care about timestamp/timezone as I am returning only dates from SQL in ISO format. To avoid the day being either one ahead or one behind when converting to Date object, this works:

moment(ISOStringHere, 'YYYY-MM-DD HH:mm'); // leaving off Z makes it UTC to match database

This requires the Moment JS library located here:

https://momentjs.com/

Answer 2

Here's a function that works well for those that need to support older browsers and adjust correctly for timezones in the date strings. I used RobG's answer as a starting point, but had to modify it heavily because it wasn't working for me with strings that had offsets for the timezone like "-07:00" (i.e. strings that don't end in "Z").

// Parse an ISO date string (i.e. "2019-01-18T00:00:00.000Z",
// "2019-01-17T17:00:00.000-07:00", or "2019-01-18T07:00:00.000+07:00",
// which are the same time) and return a JavaScript Date object with the
// value represented by the string.
function isoStringToDate( isoString ) {

    // Split the string into an array based on the digit groups.
    var dateParts = isoString.split( /\D+/ );

    // Set up a date object with the current time.
    var returnDate = new Date();

    // Manually parse the parts of the string and set each part for the
    // date. Note: Using the UTC versions of these functions is necessary
    // because we're manually adjusting for time zones stored in the
    // string.
    returnDate.setUTCFullYear( parseInt( dateParts[ 0 ] ) );

    // The month numbers are one "off" from what normal humans would expect
    // because January == 0.
    returnDate.setUTCMonth( parseInt( dateParts[ 1 ] - 1 ) );
    returnDate.setUTCDate( parseInt( dateParts[ 2 ] ) );

    // Set the time parts of the date object.
    returnDate.setUTCHours( parseInt( dateParts[ 3 ] ) );
    returnDate.setUTCMinutes( parseInt( dateParts[ 4 ] ) );
    returnDate.setUTCSeconds( parseInt( dateParts[ 5 ] ) );
    returnDate.setUTCMilliseconds( parseInt( dateParts[ 6 ] ) );

    // Track the number of hours we need to adjust the date by based
    // on the timezone.
    var timezoneOffsetHours = 0;

    // If there's a value for either the hours or minutes offset.
    if ( dateParts[ 7 ] || dateParts[ 8 ] ) {

        // Track the number of minutes we need to adjust the date by
        // based on the timezone.
        var timezoneOffsetMinutes = 0;

        // If there's a value for the minutes offset.
        if ( dateParts[ 8 ] ) {

            // Convert the minutes value into an hours value.
            timezoneOffsetMinutes = parseInt( dateParts[ 8 ] ) / 60;
        }

        // Add the hours and minutes values to get the total offset in
        // hours.
        timezoneOffsetHours = parseInt( dateParts[ 7 ] ) + timezoneOffsetMinutes;

        // If the sign for the timezone is a plus to indicate the
        // timezone is ahead of UTC time.
        if ( isoString.substr( -6, 1 ) == "+" ) {

            // Make the offset negative since the hours will need to be
            // subtracted from the date.
            timezoneOffsetHours *= -1;
        }
    }

    // Get the current hours for the date and add the offset to get the
    // correct time adjusted for timezone.
    returnDate.setHours( returnDate.getHours() + timezoneOffsetHours );

    // Return the Date object calculated from the string.
    return returnDate;
}

Usage/a couple tests:

// All three of these tests output the same date (relative to your
// timezone) as they should, which in my case is:
// "Thu Jan 17 2019 17:00:00 GMT-0700 (Mountain Standard Time)".
console.log( isoStringToDate( "2019-01-18T00:00:00.000Z" ) );
console.log( isoStringToDate( "2019-01-17T17:00:00.000-07:00" ) );
console.log( isoStringToDate( "2019-01-18T07:00:00.000+07:00" ) );