Developing Quality Metadata

30

Finding Time Values

Time values are tricky. They should fit this format, although the 12- and 24-hour versions are different:

00:00 xx

But we must take account of the range of values. The trick is to divide and conquer. The leading zero is optional, so the ? operator helps with the first digit. The second digit is problematic, but this will match 0 to 23 including whether we also have 00 as well:

[01]?[0-9]|2[0-3]

The minute values range from 00 to 59 and are matched with this:

[0-5][0-9]

Putting it all together with the colon and adding seconds values we get this:

([01]?[0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9])

For a 12-hour clock with ...