Unexpected behavior: Angular4/Javascript Date object alters when timezone is specified in Date constructor

Question

Unexpected behavior: Angular4/Javascript Date object alters when timezone is specified in Date constructor

In my Angular 4 application, I encountered an issue with a date retrieved from an API call. The date is in the format '1990-03-31T23:00:00-06:00' and when attempting to create a Date object and retrieve the month using getMonth(), it returns the wrong day. After investigating in the console:

> var x = new Date('1990-03-31T23:00:00-06:00');
undefined
 > x
Sun Apr 01 1990 00:00:00 GMT-0500 (Central Daylight Time)
> var x = new Date('1990-03-31T23:00:00');
Sat Mar 31 1990 23:00:00 GMT-0500 (Central Daylight Time)
> new Date().getTimezoneOffset();
360

Upon examining my code:

new Date(this.bsSelected.StatementDate).getMonth()

I am unsure of why this discrepancy is occurring and how to resolve it. As a temporary fix, I have removed the TimeZone information from the API output, but I am curious if there is a better solution once I understand the root cause of the problem.

javascript angular date

Answer 1

Answer №1

There are no changes being made. The input

new Date('1990-03-31T23:00:00-06:00')

conforms to the valid ISO 8601 format and will be correctly interpreted by modern web browsers (although not older ones).

The timestamp "Sun Apr 01 1990 00:00:00 GMT-0500 (Central Daylight Time)" actually corresponds to the same exact moment as "1990-03-31T23:00:00-06:00", but in a different timezone. Your computer settings appear to have daylight saving adjustments for that specific date, hence the variation in time zones.

Recent editions of ECMA-262 mandate software implementations to accommodate historical changes in timezones. Given the myriad alterations over the years, it's inaccurate to assume that current regulations have always been in effect (as some prior versions of ECMA-262 stipulated).

new Date().getTimezoneOffset()

This function retrieves the local timezone offset for the present date and time, which might differ from the offset for another point in time.

What is the rationale behind removing the timezone information? The recommended approach involves utilizing Coordinated Universal Time (UTC) consistently and only resorting to local values when displaying dates and times to users. Without more context regarding your use case for the date, it's difficult to determine the most suitable solution. Eliminating the timezone works well only if everything should adhere to the same (host-defined) timezone. Alternatively, complications may arise.

Maintaining a uniform offset during daylight saving time transitions will not be resolved by discarding the timezone information.

Furthermore, it's important to note that certain web browsers exhibit parsing glitches (such as Safari). By stripping the timezone element (e.g. "1990-03-31T23:00:00"), the string will be perceived as UTC rather than local time.

Answer 2

There are no changes being made. The input

new Date('1990-03-31T23:00:00-06:00')

conforms to the valid ISO 8601 format and will be correctly interpreted by modern web browsers (although not older ones).

The timestamp "Sun Apr 01 1990 00:00:00 GMT-0500 (Central Daylight Time)" actually corresponds to the same exact moment as "1990-03-31T23:00:00-06:00", but in a different timezone. Your computer settings appear to have daylight saving adjustments for that specific date, hence the variation in time zones.

Recent editions of ECMA-262 mandate software implementations to accommodate historical changes in timezones. Given the myriad alterations over the years, it's inaccurate to assume that current regulations have always been in effect (as some prior versions of ECMA-262 stipulated).

new Date().getTimezoneOffset()

This function retrieves the local timezone offset for the present date and time, which might differ from the offset for another point in time.

What is the rationale behind removing the timezone information? The recommended approach involves utilizing Coordinated Universal Time (UTC) consistently and only resorting to local values when displaying dates and times to users. Without more context regarding your use case for the date, it's difficult to determine the most suitable solution. Eliminating the timezone works well only if everything should adhere to the same (host-defined) timezone. Alternatively, complications may arise.

Maintaining a uniform offset during daylight saving time transitions will not be resolved by discarding the timezone information.

Furthermore, it's important to note that certain web browsers exhibit parsing glitches (such as Safari). By stripping the timezone element (e.g. "1990-03-31T23:00:00"), the string will be perceived as UTC rather than local time.

Answer 3

Answer №2

Your browser may show a different date due to being in a different GMT time zone, making it appear as the 1st of April instead of the actual date. If the date in GMT-0600 is March 31, 1990, your browser may display it as April 1, 1990.

To see the timestamp without the offset part affecting it, you can remove the offset from the string, and the browser will use that timestamp as the current time.

Here is an example:

console.log('With timezone:', new Date('1990-03-31T23:00:00-06:00').getMonth());

console.log('Without timezone:', new Date('1990-03-31T23:00:00').getMonth());

Note: getMonth() returns a number between 0 and 11.

Answer 4

Your browser may show a different date due to being in a different GMT time zone, making it appear as the 1st of April instead of the actual date. If the date in GMT-0600 is March 31, 1990, your browser may display it as April 1, 1990.

To see the timestamp without the offset part affecting it, you can remove the offset from the string, and the browser will use that timestamp as the current time.

Here is an example:

console.log('With timezone:', new Date('1990-03-31T23:00:00-06:00').getMonth());

console.log('Without timezone:', new Date('1990-03-31T23:00:00').getMonth());

Note: getMonth() returns a number between 0 and 11.

Answer 5

Answer №3

When working with the Date object in JavaScript, it automatically converts to your local timezone. If you wish to remove the timezone information, simply follow the approach you are currently using. For those who require preserving timezone data, consider utilizing a third-party library such as Moment Timezone.

Answer 6

When working with the Date object in JavaScript, it automatically converts to your local timezone. If you wish to remove the timezone information, simply follow the approach you are currently using. For those who require preserving timezone data, consider utilizing a third-party library such as Moment Timezone.

Unexpected behavior: Angular4/Javascript Date object alters when timezone is specified in Date constructor

Answer №1

Answer №2

Answer №3

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