Infovark Underground

I needed a regular expression to correctly parse ISO 8601 format dates and times. The standard includes many alternative representations, but I was particularly concerned about the subset of ISO 8601 formats allowed in XML.

Paul Ward had posted a date parsing expression on the RegExLib site. I extended it a bit to handle times and time zones. I’m pretty sure they work, though it can be hard to tell sometimes. (See Jeff Atwood’s Now You Have Two Problems.)

ISO date
^(\d{4})\D?(0[1-9]|1[0-2])\D?([12]\d|0[1-9]|3[01])$

ISO time
^([01]\d|2[0-3])\D?([0-5]\d)\D?([0-5]\d)?\D?(\d{3})?$

ISO offset
^([zZ]|([\+-])([01]\d|2[0-3])\D?([0-5]\d)?)?$

ISO date and time
^(\d{4})\D?(0[1-9]|1[0-2])\D?([12]\d|0[1-9]|3[01])(\D?([01]\d|2[0-3])\D?([0-5]\d)\D?([0-5]\d)?\D?(\d{3})?)?$

ISO date, time, and offset (the works)
^(\d{4})\D?(0[1-9]|1[0-2])\D?([12]\d|0[1-9]|3[01])(\D?([01]\d|2[0-3])\D?([0-5]\d)\D?([0-5]\d)?\D?(\d{3})?([zZ]|([\+-])([01]\d|2[0-3])\D?([0-5]\d)?)?)?$

If you find it useful — or find a bug — let me know.