Seconds - Freq="SECONDLY", BYSECOND
Minutes - Freq="MINUTELY", BYMINUTE
Hours -   Freq="HOURLY",   BYHOUR
Days -    Freq="DAILY",    BYDAY, BYMONTHDAY, BYYEARDAY
Weeks -   Freq="WEEKLY",   BYWEEKNO
Months -  Freq="MONTHLY",  BYMONTH
Years -   Freq="YEARLY"