Regular Expressions Cookbook

4.7. Validate ISO 8601 Dates and Times

Problem

You want to match dates and/or times in the official ISO 8601 format, which is the basis for many standardized date and time formats. For example, in XML Schema, the built-in date, time, and dateTime types are all based on ISO 8601.

Solution

The following matches a calendar month, e.g., 2008-08. The hyphen is required:

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

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

^(?<year>[0-9]{4})-(?<month>1[0-2]|0[1-9])$

Regex options: None

Regex flavors: .NET, PCRE 7, Perl 5.10, Ruby 1.9

^(?P<year>[0-9]{4})-(?P<month>1[0-2]|0[1-9])$

Regex options: None

Regex flavors: PCRE, Python

Calendar date, e.g., 2008-08-30. The hyphens are optional. This regex allows YYYY-MMDD and YYYYMM-DD, which do not follow ISO 8601:

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

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

^(?<year>[0-9]{4})-?(?<month>1[0-2]|0[1-9])-?↵
(?<day>3[0-1]|0[1-9]|[1-2][0-9])$

Regex options: None

Regex flavors: .NET, PCRE 7, Perl 5.10, Ruby 1.9

Calendar date, e.g., 2008-08-30. The hyphens are optional. This regex uses a conditional to exclude YYYY-MMDD and YYYYMM-DD. There is an extra capturing group for the first hyphen:

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

Regex options: None

Regex flavors: .NET, PCRE, Perl, Python

Calendar date, e.g., 2008-08-30. The hyphens are optional. This regex uses alternation to exclude YYYY-MMDD and ...