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

[0-9]{4}-[0-9]{2}-[0-9]{2}

or

\d\d\d\d-\d\d-\d\d

or

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simply read first regex tutorial