Date

Valid date

Any valid date from the year 1000 onwards.

[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])

This is too simple to validate February, but it allows a month to have up to 31 days.

Test strings

Match

1000-01-01
2017-01-01
2019-02-12
2020-03-30
2999-12-31

Don’t match

0123-01-01
2020-13-01
2020-12-32
2020-12-40