The majority of Sikhs, since 1999, uses the Nanakshahi calendar which always starts on March 14th, and has 5 months of 31 days followed by 6 months of 30 days (the last month is 30 days on Gregorian non-leap years and 31 days on Gregorian leap years).
Note that some small part of the Sikh community may still follow a lunar calendar, as used in determining Hindu dates in India. These holidays rules should be setup using Hindu recurrence rules. When using the Hindu Lunar calendar, a holiday rule can be found by selecting dates when this holiday occurred and using the Holidays Rule Wizard, with the Hindu Lunar rule that matches.
See also: Recurrence Rules Options.