A fully tested regex that extracts and validates date parts using named capturing groups.

Validations:

• Year must be preceded by nothing or a non-digit character
• Year must have 4 digits
• Month must be between 01 and 12
• Month must have 2 digits
• Day must be between 01 and the maximum number of days for the month (e.g. february can't have more than 29 days)
• Day must have 2 digits
• Day must be followed by nothing or a non-digit character
• Separator must be any single character that is not a space or an alphanumeric character
• Separator must be the same between each date part

Capturing groups:

| # |   Name  | Description                         |
|:-:|:-------:|-------------------------------------|
| 1 |  `year` | 4 digits of the year                |
| 2 |  `sep`  | Date parts separator                |
| 3 | `month` | 2 digits of the month               |
| 4 |  `day`  | 2 digits of the date (day of month) |

Example usage:

let match = regex.exec('2020-11-22')

console.log('year: %s, month: %s, day: %s',
            match.groups.year,
            match.groups.month,
            match.groups.day)

// year: 2020, month: 11, day: 22

Compatibility: (updated 2020-11-20)

• Chrome >= 64
• Edge >= 79
• Firefox >= 78
• IE incompatible (lookbehind assertions & named capture groups not supported)
• Opera >= 51
• Safari incompatible (lookbehind assertions not supported)
• NodeJS >= 10.0.0

See regex compatibility table.

Note: does not validate leap years (not really possible in regex)