repeat_interval = regular_schedule | combined_schedule

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regular_schedule = frequency_clause

[";" interval_clause] [";" bymonth_clause] [";" byweekno_clause]

[";" byyearday_clause] [";" bydate_clause] [";" bymonthday_clause]

[";" byday_clause] [";" byhour_clause] [";" byminute_clause]

[";" bysecond_clause] [";" bysetpos_clause] [";" include_clause]

[";" exclude_clause] [";" intersect_clause][";" periods_clause]

[";" byperiod_clause]

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combined_schedule = schedule_list [";" include_clause]

[";" exclude_clause] [";" intersect_clause]

frequency_clause = "FREQ" "=" ( predefined_frequency | user_defined_frequency )

predefined_frequency = "YEARLY" | "MONTHLY" | "WEEKLY" | "DAILY" | 

   "HOURLY" | "MINUTELY" | "SECONDLY"

user_defined_frequency = named_schedule

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interval_clause = "INTERVAL" "=" intervalnum

   intervalnum = 1 through 99

bymonth_clause = "BYMONTH" "=" monthlist

   monthlist = monthday ( "," monthday)*

   month = numeric_month | char_month

   numeric_month = 1 | 2 | 3 ...  12

   char_month = "JAN" | "FEB" | "MAR" | "APR" | "MAY" | "JUN" |

   "JUL" | "AUG" | "SEP" | "OCT" | "NOV" | "DEC"

byweekno_clause = "BYWEEKNO" "=" weeknumber_list

   weeknumber_list = weeknumber ( "," weeknumber)*

   weeknumber = [minus] weekno

   weekno = 1 through 53

byyearday_clause = "BYYEARDAY" "=" yearday_list

   yearday_list = yearday ( "," yearday)*

   yearday = [minus] yeardaynum

   yeardaynum = 1 through 366

bydate_clause = "BYDATE" "=" date_list

   date_list = date ( "," date)*

   date = [YYYY]MMDD [ offset | span ]

bymonthday_clause = "BYMONTHDAY" "=" monthday_list

   monthday_list = monthday ( "," monthday)*

   monthday = [minus] monthdaynum

   monthdaynum = 1 through 31

byday_clause = "BYDAY" "=" byday_list

   byday_list = byday ( "," byday)*

   byday = [weekdaynum] day

   weekdaynum = [minus] daynum

   daynum = 1 through 53 /* if frequency is yearly */

   daynum = 1 through 5  /* if frequency is monthly */

   day = "MON" | "TUE" | "WED" | "THU" | "FRI" | "SAT" | "SUN"

byhour_clause = "BYHOUR" "=" hour_list

   hour_list = hour ( "," hour)*

   hour = 0 through 23

byminute_clause = "BYMINUTE" "=" minute_list

   minute_list = minute ( "," minute)*

   minute = 0 through 59

bysecond_clause = "BYSECOND" "=" second_list

   second_list = second ( "," second)*

   second = 0 through 59

bysetpos_clause = "BYSETPOS" "=" setpos_list

   setpos_list = setpos ("," setpos)*

   setpos = [minus] setpos_num

   setpos_num = 1 through 9999

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include_clause = "INCLUDE" "=" schedule_list

exclude_clause = "EXCLUDE" "=" schedule_list

intersect_clause = "INTERSECT" "=" schedule_list

schedule_list = schedule_clause ("," schedule_clause)*

schedule_clause = named_schedule [ offset ]

named_schedule = [schema "."] schedule

periods_clause = "PERIODS" "=" periodnum

byperiod_clause = "BYPERIOD" "=" period_list

period_list = periodnum ("," periodnum)*

periodnum = 1 through 100

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offset = ("+" | "-") ["OFFSET:"] duration_val

span = ("+" | "-" | "^") "SPAN:" duration_val

duration_val = dur-weeks | dur_days

dur_weeks = numofweeks "W"

dur_days = numofdays "D"

numofweeks = 1 through 53

numofdays = 1 through 376

REPEAT_INTERVAL => ¨FREQ=DAILY; BYDAY=FRI¨;

REPEAT_INTERVAL => ¨FREQ=WEEKLY; BYDAY=FRI¨;