Add support for iCal BYDAY (1TU or -1FR) rrules in Calendar

[imJexs]

One of the biggest things that has turned me away from the IPS Calendar over the years is the lack of support for iCal RRULE BYDAY.

Our community has many events that occur on the first Wednesday of the month, third Saturday of the month, or fifth Thursday of the month (this is a rare occurrence but it happens). Adding support for these edge cases would be amazing and it would also make IPS Calendar more compatible with importing Calendars from other providers like Google Calendar as well as exporting to Google Calendar which would be extremely useful for our members.

I did notice that the following comments:

//@todo	[Future] We do not support HOURLY, MINUTELY or SECONDLY "FREQ" values
//@todo	[Future] We do not support the properties BYSETPOS, BYYEARDAY, BYMONTH, BYHOUR, BYMINUTE, BYSECOND, BYWEEKNO, WKST
//@todo	[Future] We do not support complex BYDAY values, such as 1TU or -1FR
//@todo	[Future] We do not support multiple values for BYMONTHDAY, nor do we support negative values

were included in:

\IPS\Calendar\Icalendar\ICSParser::parseRrule()

which is very exciting, I'm just hoping we could get this added sooner rather than later.

Best Regards,
Jexs

[bfarber]

It is challenging from a performance perspective to implement these without potentially causing issues, however it is on our radar (as you can see from the code comments).