55 lines
1.6 KiB
Markdown
55 lines
1.6 KiB
Markdown
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# Unicode Tokens
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Starting with v2, `format` and `parse` use [Unicode tokens].
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The tokens are different from Moment.js and other libraries that opted to use
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custom formatting rules. While usage of a standard ensures compatibility and
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the future of the library, it causes confusion that this document intends
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to resolve.
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## Popular mistakes
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There are 4 tokens that cause most of the confusion:
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- `D` and `DD` that represent the day of a year (1, 2, ..., 365, 366)
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are often confused with `d` and `dd` that represent the day of a month
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(1, 2, ..., 31).
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- `YY` and `YYYY` that represent the local week-numbering year (44, 01, 00, 17)
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are often confused with `yy` and `yyyy` that represent the calendar year.
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```js
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// ❌ Wrong!
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format(new Date(), 'YYYY-MM-DD')
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//=> 2018-10-283
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// ✅ Correct
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format(new Date(), 'yyyy-MM-dd')
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//=> 2018-10-10
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// ❌ Wrong!
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parse('11.02.87', 'D.MM.YY', new Date()).toString()
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//=> 'Sat Jan 11 1986 00:00:00 GMT+0200 (EET)'
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// ✅ Correct
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parse('11.02.87', 'd.MM.yy', new Date()).toString()
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//=> 'Wed Feb 11 1987 00:00:00 GMT+0200 (EET)'
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```
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To help with the issue, `format` and `parse` functions won't accept
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these tokens without `useAdditionalDayOfYearTokens` option for `D` and `DD` and
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`useAdditionalWeekYearTokens` options for `YY` and `YYYY`:
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```js
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format(new Date(), 'D', { useAdditionalDayOfYearTokens: true })
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//=> '283'
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parse('365+1987', 'DD+YYYY', new Date(), {
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useAdditionalDayOfYearTokens: true,
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useAdditionalWeekYearTokens: true
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}).toString()
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//=> 'Wed Dec 31 1986 00:00:00 GMT+0200 (EET)'
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```
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[Unicode tokens]: https://www.unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
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