Correct Regular expressions to match a date

Question

What is the correct regular expression to use to validate a date like. 2009-10-22 or 2009-01-01 etc. Platform PHP

Answer 1

For a complete validation (which would include verifying that the day, month and year parts are valid) a Regex is not the tool of choice. Apart from month issues you'd get into trouble with leap years...

So, if you just want to check if the rough format is correct, or isolate the different parts (year-month-day), a regex is fine.

([0-9]{1,4})-(1[012]|0?[1-9])-([12][0-9]|3[01]|0?[1-9])

This is already pretty exact and captures the year (0..9999), month and day into capture groups, ready for parsing...