public Class Recur<T extends Temporal>

    3.3.10.  Recurrence Rule

   Value Name:  RECUR

   Purpose:  This value type is used to identify properties that contain
      a recurrence rule specification.

   Format Definition:  This value type is defined by the following
      notation:

       recur           = recur-rule-part *( ";" recur-rule-part )
                       ;
                       ; The rule parts are not ordered in any
                       ; particular sequence.
                       ;
                       ; The FREQ rule part is REQUIRED,
                       ; but MUST NOT occur more than once.
                       ;
                       ; The UNTIL or COUNT rule parts are OPTIONAL,
                       ; but they MUST NOT occur in the same 'recur'.
                       ;

                       ; The other rule parts are OPTIONAL,
                       ; but MUST NOT occur more than once.

       recur-rule-part = ( "FREQ" "=" freq )
                       / ( "UNTIL" "=" enddate )
                       / ( "COUNT" "=" 1*DIGIT )
                       / ( "INTERVAL" "=" 1*DIGIT )
                       / ( "BYSECOND" "=" byseclist )
                       / ( "BYMINUTE" "=" byminlist )
                       / ( "BYHOUR" "=" byhrlist )
                       / ( "BYDAY" "=" bywdaylist )
                       / ( "BYMONTHDAY" "=" bymodaylist )
                       / ( "BYYEARDAY" "=" byyrdaylist )
                       / ( "BYWEEKNO" "=" bywknolist )
                       / ( "BYMONTH" "=" bymolist )
                       / ( "BYSETPOS" "=" bysplist )
                       / ( "WKST" "=" weekday )

       freq        = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
                   / "WEEKLY" / "MONTHLY" / "YEARLY"

       enddate     = date / date-time

       byseclist   = ( seconds *("," seconds) )

       seconds     = 1*2DIGIT       ;0 to 60

       byminlist   = ( minutes *("," minutes) )

       minutes     = 1*2DIGIT       ;0 to 59

       byhrlist    = ( hour *("," hour) )

       hour        = 1*2DIGIT       ;0 to 23

       bywdaylist  = ( weekdaynum *("," weekdaynum) )

       weekdaynum  = [[plus / minus] ordwk] weekday

       plus        = "+"

       minus       = "-"

       ordwk       = 1*2DIGIT       ;1 to 53

       weekday     = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
       ;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
       ;FRIDAY, and SATURDAY days of the week.

       bymodaylist = ( monthdaynum *("," monthdaynum) )

       monthdaynum = [plus / minus] ordmoday

       ordmoday    = 1*2DIGIT       ;1 to 31

       byyrdaylist = ( yeardaynum *("," yeardaynum) )

       yeardaynum  = [plus / minus] ordyrday

       ordyrday    = 1*3DIGIT      ;1 to 366

       bywknolist  = ( weeknum *("," weeknum) )

       weeknum     = [plus / minus] ordwk

       bymolist    = ( monthnum *("," monthnum) )

       monthnum    = 1*2DIGIT       ;1 to 12

       bysplist    = ( setposday *("," setposday) )

       setposday   = yeardaynum