I'm trying to make an iCal feed (RFC 2445) for work holidays that won't need yearly updates, by listing holidays per their definition, rather than which dates they occur on on particular years.
Holidays like Memorial day (last Monday in May) of course don't need any special treatment beyond
BEGIN:VEVENT
DTSTAMP:20130210T211949Z
UID:[email protected]
DTSTART;VALUE=DATE:20130527
DTEND;VALUE=DATE:20130527
SUMMARY:Memorial Day
RRULE:FREQ=YEARLY;BYMONTH=5;BYDAY=-1MO;WKST=SU
END:VEVENT...but when it comes to date-based holidays like New Year's Day, how does one encode the day slip on weekend Jan 1sts?
you should be aware that even though google calendar follows RFC2445, it has been obsoleted by RFC5545 which has made the EXRULE obsolete (deprecated features from RFC2445).
in the case of UK new year, it is:
BEGIN:VCALENDAR
VERSION:2.0
METHOD:PUBLISH
PRODID:pyICSParser
BEGIN:VEVENT
DTSTART;VALUE=DATE:20070101
RRULE:FREQ=YEARLY;BYMONTH=1;BYDAY=MO,TU,WE,TH,FR;BYMONTHDAY=1,2,3;BYSETPOS=1
UID:[email protected]
DTSTAMP:19970714T170000Z
SUMMARY: new year
END:VEVENT
END:VCALENDAR
which works like a charm under google calendar, outlook.com(/hotmail/...), yahoo calendars and on iOS devices synching from a Google Calendar.
UPDATE: for the USA new year
it would be a combination of 2 RRULE (RFC says SHOULD NOT occur more than once which seems to leave the possibility of 2 RRULE by event:
RRULE:FREQ=YEARLY;BYMONTH=1;BYDAY=MO,TU,WE,TH,FR;BYMONTHDAY=1,2;BYSETPOS=1
RRULE:FREQ=YEARLY;BYMONTH=12;BYDAY=FR;BYMONTHDAY=-1
Google Calendar supports it but looks like yahoo and hotmail/outlook.com don't, so 2 events would need to be created (one with each RRULE). If needed the use of RELATED-TO property could help keep track of their relations.