Moment js parse utc8/26/2023 ![]() The value of an absent time zone offset is "Z"Įffectively what this means is that ISO 8601 dates without an offset are to be treated as UTC values, creating the following oddity: //US local format var a = new Date( '') In addition, the ECMA Script 5 Specification makes an unusual assertion about the offset of ISO 8601 dates: Moment's parser handles it just fine though: moment( '', 'DD/MM/YYYY', true).format() There is no good work-around for this behavior with the native Date object. var a = new Date( '') //Decemin DD/MM/YYYY format //"Tue 00:00:00 GMT-0600 (Central Standard Time)" For instance, suppose I am using a computer in the United States, but I have a date in DD/MM/YYYY format. ![]() Parsing is notably unpredictable with native date. In doing this, Moment.js extends the functionality and also accounts for several deficiencies in the object. ![]() Moment.js provides a wrapper for the native JavaScript date object. It does not provide support for adjusting dates based on time zone data - this is provided by the Moment TimeZone library.įor an in depth description of this issue, see the Stack Overflow tag. The Moment.js core library provides functionality related to adjusting times based on an offset value. ![]() For this reason, it is impossible to infer a time zone from just an offset value. For example, the time zones America/Chicago, America/Denver, and America/Belize all have an offset of -06:00 at varying times. Several time zones may have the same offset at some point during the year. It is expressed in the format HH:mm most of the time.Ī time zone is a geographical region where all people observe a legally mandated standard time.Ī time zone usually has more than one offset from UTC due to daylight saving time. Moment().add( 1.5, 'quarters') = moment().add( 4.5, 'months') = moment().add( 5, 'months') Time Zone vs Offsetįrequently, people are confused about the difference between time zones and UTC offsets.Ī UTC offset is a value that represents how far a particular date and time is from UTC. Quarters and years are converted to months, and then absolute value/rounded. This means that 1.5 rounds to 2, and -1.5 rounds to -2. Moment.js will accept decimal values and do its best to handle them by rounding to the nearest whole number.Īs of 2.12.0 decimal day and month values use absolute value/round to convert to integers. Moment( '').add( 365, 'day').format( 'LL')īecause of the variability of duration in day math, Moment's API does not officially support adding or subtracting decimal values for days and larger. Date math can cause some interesting scenarios.ĭue to daylight saving time, one day may not equal 24 hours: //date math Months of course vary in number of days, and due to leap year, years vary in length as well. For example, due to daylight saving time transition, a day may be anywhere between 23 and 25 hours long. This is because the amount of time in a day, month, or year is variable. In Moment.js time math assumes a linear time scale, just incrementing or decrementing the UTC-based timestamp by the amount of the time units provided.ĭate math does not use a linear time scale, but rather increments or decrements the dates on the calendar. There is a logical difference between time math and date math. To avoid situations like that, clone the moment before performing date math: var a = moment( '') When first using Moment.js many developers are confused by scenarios like this: var a = moment( '') Īs you can see, adding one week mutated a. This means that operations like add, subtract, or set change the original moment object. The moment object in Moment.js is mutable. If you have a request for a guide that you would like to see here, or would like to add a guide please create an issue or make a pull request in the repository. The guides section is new and still under construction. We address our most frequently seen support requests here, so it is a great place to check for solutions to any issues you may have. The guides area is designed to help developers learn to better interact with the date and time problem domain, and the Moment.js library.
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