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