The following lists the expected format and details of our rrules:

* DTSTART is required and must follow the following format: DTSTART:YYYYMMDDTHHMMSSZ
* DTSTART is expected to be in UTC
* INTERVAL is required
* SECONDLY is not supported
* TZID is not supported
* RRULE must preceed the rule statements
* BYDAY is supported but not BYDAY with a numerical prefix
* BYYEARDAY and BYWEEKNO are not supported
* Only one rrule statement per schedule is supported
* COUNT must be < 1000

Here are some example rrules:

    "DTSTART:20500331T055000Z RRULE:FREQ=MINUTELY;INTERVAL=10;COUNT=5"
    "DTSTART:20240331T075000Z RRULE:FREQ=DAILY;INTERVAL=1;COUNT=1"
    "DTSTART:20140331T075000Z RRULE:FREQ=MINUTELY;INTERVAL=1;UNTIL=20230401T075000Z"
    "DTSTART:20140331T075000Z RRULE:FREQ=WEEKLY;INTERVAL=1;BYDAY=MO,WE,FR"
    "DTSTART:20140331T075000Z RRULE:FREQ=WEEKLY;INTERVAL=5;BYDAY=MO"
    "DTSTART:20140331T075000Z RRULE:FREQ=MONTHLY;INTERVAL=1;BYMONTHDAY=6"
    "DTSTART:20140331T075000Z RRULE:FREQ=MONTHLY;INTERVAL=1;BYSETPOS=4;BYDAY=SU"
    "DTSTART:20140331T075000Z RRULE:FREQ=MONTHLY;INTERVAL=1;BYSETPOS=-1;BYDAY=MO,TU,WE,TH,FR"
    "DTSTART:20140331T075000Z RRULE:FREQ=MONTHLY;INTERVAL=1;BYSETPOS=-1;BYDAY=MO,TU,WE,TH,FR,SA,SU"
    "DTSTART:20140331T075000Z RRULE:FREQ=YEARLY;INTERVAL=1;BYMONTH=4;BYMONTHDAY=1"
    "DTSTART:20140331T075000Z RRULE:FREQ=YEARLY;INTERVAL=1;BYSETPOS=-1;BYMONTH=8;BYDAY=SU"
    "DTSTART:20140331T075000Z RRULE:FREQ=WEEKLY;INTERVAL=1;UNTIL=20230401T075000Z;BYDAY=MO,WE,FR"
    "DTSTART:20140331T075000Z RRULE:FREQ=HOURLY;INTERVAL=1;UNTIL=20230610T075000Z"
