FA-77086 / Calendar recurrence rules / Open access

Daily BYHOUR/BYMINUTE time-of-day expansion: hour normalization · case 01

BYHOUR=17,9 emits the evening slot before the morning slot and repeats duplicated hours.

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ROOT CAUSE

The BYHOUR list is used as given, unsorted and with duplicates.

VERIFIED REPAIR

At the hour normalization decision use `sorted(set(byhour))`, leaving the other decision sites of the model unchanged.

Unsuccessful approach: The partial repair `sorted(byhour)` sorts but keeps duplicate hours, producing repeated instances.

Case contract

FREQ=DAILY. Each day produces the cartesian product of BYHOUR and BYMINUTE in chronological order; a missing BYHOUR defaults to the dtstart hour and a missing BYMINUTE to the dtstart minute. Duplicates in either list are ignored. Times before dtstart are dropped. Return the first count ISO date-times.

Why this case matters

Recurring calendar series are expanded into concrete instances for display, reminders and conflict checks.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime as dt
import calendar
N = 1
observations = []
def solve(dtstart, byhour, byminute, count):
    first = dt.datetime.fromisoformat(dtstart)
    hours = list(byhour) if byhour else [first.hour]
    minutes = sorted(set(byminute)) if byminute else [first.minute]
    out = []
    for k in range(400):
        day = first.date() + dt.timedelta(days=k)
        for h, mi in [(h, mi) for h in hours for mi in minutes]:
            t = dt.datetime.combine(day, dt.time(h, mi))
            if t < first:
                continue
            if len(out) >= count:
                return out
            out.append(t.isoformat(timespec='minutes'))
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']),
  ('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05'])],
 [('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']),
  ('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists',
   ['2024-02-28T23:45', [], [], 3],
   ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45'])],
 [('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15'])],
 [('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15'])],
 [('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
regression: default minute from dtstart	`['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']`	`['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']`	Passed
only byminute	`['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']`	`['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']`	Passed
unsorted duplicate hours	`['2024-01-01T17:15', '2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T17:15']`	`['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']`	Failed
product of two lists	`['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']`	`['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']`	Passed
dtstart after some slots	`['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']`	`['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']`	Passed
dtstart between minutes	`['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']`	`['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']`	Passed
three by three	`['2024-03-10T06:05', '2024-03-10T06:10', '2024-03-10T06:50', '2024-03-10T12:05', '2024-03-10T12:10', '2024-03-10T12:50', '2024-03-10T18:05']`	`['2024-03-10T06:05', '2024-03-10T06:10', '2024-03-10T06:50', '2024-03-10T12:05', '2024-03-10T12:10', '2024-03-10T12:50', '2024-03-10T18:05']`	Passed

SHA-256 / 11be287bca46c30255cd28f9130633bcc3ca977d6b720b233e6d9b7019725b35

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime as dt
import calendar
N = 1
observations = []
def solve(dtstart, byhour, byminute, count):
    first = dt.datetime.fromisoformat(dtstart)
    hours = sorted(byhour) if byhour else [first.hour]
    minutes = sorted(set(byminute)) if byminute else [first.minute]
    out = []
    for k in range(400):
        day = first.date() + dt.timedelta(days=k)
        for h, mi in [(h, mi) for h in hours for mi in minutes]:
            t = dt.datetime.combine(day, dt.time(h, mi))
            if t < first:
                continue
            if len(out) >= count:
                return out
            out.append(t.isoformat(timespec='minutes'))
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']),
  ('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05'])],
 [('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']),
  ('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists',
   ['2024-02-28T23:45', [], [], 3],
   ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45'])],
 [('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15'])],
 [('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15'])],
 [('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
regression: default minute from dtstart	`['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']`	`['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']`	Passed
only byminute	`['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']`	`['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']`	Passed
unsorted duplicate hours	`['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-01T17:15', '2024-01-02T09:15']`	`['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']`	Failed
product of two lists	`['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']`	`['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']`	Passed
dtstart after some slots	`['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']`	`['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']`	Passed
dtstart between minutes	`['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']`	`['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']`	Passed
three by three	`['2024-03-10T06:05', '2024-03-10T06:10', '2024-03-10T06:50', '2024-03-10T12:05', '2024-03-10T12:10', '2024-03-10T12:50', '2024-03-10T18:05']`	`['2024-03-10T06:05', '2024-03-10T06:10', '2024-03-10T06:50', '2024-03-10T12:05', '2024-03-10T12:10', '2024-03-10T12:50', '2024-03-10T18:05']`	Passed

SHA-256 / ea518baea2606db2b8fe8f83c4f83f499beb9f717dc5484ec271a84fc892c653

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime as dt
import calendar
N = 1
observations = []
def solve(dtstart, byhour, byminute, count):
    first = dt.datetime.fromisoformat(dtstart)
    hours = sorted(set(byhour)) if byhour else [first.hour]
    minutes = sorted(set(byminute)) if byminute else [first.minute]
    out = []
    for k in range(400):
        day = first.date() + dt.timedelta(days=k)
        for h, mi in [(h, mi) for h in hours for mi in minutes]:
            t = dt.datetime.combine(day, dt.time(h, mi))
            if t < first:
                continue
            if len(out) >= count:
                return out
            out.append(t.isoformat(timespec='minutes'))
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']),
  ('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05'])],
 [('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']),
  ('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists',
   ['2024-02-28T23:45', [], [], 3],
   ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45'])],
 [('dtstart after some slots',
   ['2024-01-02T12:00', [8, 12, 18], [0], 4],
   ['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']),
  ('dtstart between minutes',
   ['2024-01-02T12:20', [12], [0, 20, 40], 4],
   ['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']),
  ('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15'])],
 [('three by three',
   ['2024-03-10T00:00', [6, 12, 18], [5, 10, 50], 7],
   ['2024-03-10T06:05',
    '2024-03-10T06:10',
    '2024-03-10T06:50',
    '2024-03-10T12:05',
    '2024-03-10T12:10',
    '2024-03-10T12:50',
    '2024-03-10T18:05']),
  ('count zero', ['2024-01-01T09:00', [9], [0], 0], []),
  ('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15'])],
 [('no lists', ['2024-02-28T23:45', [], [], 3], ['2024-02-28T23:45', '2024-02-29T23:45', '2024-03-01T23:45']),
  ('unsorted minutes',
   ['2024-02-28T07:00', [7, 8], [50, 10], 5],
   ['2024-02-28T07:10', '2024-02-28T07:50', '2024-02-28T08:10', '2024-02-28T08:50', '2024-02-29T07:10']),
  ('late hour only list',
   ['2024-05-05T22:15', [23, 1], [], 4],
   ['2024-05-05T23:15', '2024-05-06T01:15', '2024-05-06T23:15', '2024-05-07T01:15']),
  ('regression: default minute from dtstart',
   ['2024-01-01T09:30', [9, 17], [], 4],
   ['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']),
  ('only byminute',
   ['2024-01-01T14:10', [], [0, 30], 4],
   ['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']),
  ('unsorted duplicate hours',
   ['2024-01-01T08:00', [17, 9, 17], [15], 4],
   ['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']),
  ('product of two lists',
   ['2024-01-01T00:00', [9, 13], [0, 45], 5],
   ['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
regression: default minute from dtstart	`['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']`	`['2024-01-01T09:30', '2024-01-01T17:30', '2024-01-02T09:30', '2024-01-02T17:30']`	Passed
only byminute	`['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']`	`['2024-01-01T14:30', '2024-01-02T14:00', '2024-01-02T14:30', '2024-01-03T14:00']`	Passed
unsorted duplicate hours	`['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']`	`['2024-01-01T09:15', '2024-01-01T17:15', '2024-01-02T09:15', '2024-01-02T17:15']`	Passed
product of two lists	`['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']`	`['2024-01-01T09:00', '2024-01-01T09:45', '2024-01-01T13:00', '2024-01-01T13:45', '2024-01-02T09:00']`	Passed
dtstart after some slots	`['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']`	`['2024-01-02T12:00', '2024-01-02T18:00', '2024-01-03T08:00', '2024-01-03T12:00']`	Passed
dtstart between minutes	`['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']`	`['2024-01-02T12:20', '2024-01-02T12:40', '2024-01-03T12:00', '2024-01-03T12:20']`	Passed
three by three	`['2024-03-10T06:05', '2024-03-10T06:10', '2024-03-10T06:50', '2024-03-10T12:05', '2024-03-10T12:10', '2024-03-10T12:50', '2024-03-10T18:05']`	`['2024-03-10T06:05', '2024-03-10T06:10', '2024-03-10T06:50', '2024-03-10T12:05', '2024-03-10T12:10', '2024-03-10T12:50', '2024-03-10T18:05']`	Passed

SHA-256 / 9f39fd235cc0fa4db8ace75edb2937cf2b9bfc2a4185372a25745116e4df9e93

Verification & scope

Stipulated, bounded recurrence-expansion model evaluated offline on explicit fixtures; it is not a complete iCalendar implementation and makes no claim of standards conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:49:22.329137+00:00.

Case digest / 7b6e6b92360cae8eca3046437d3ee65f1688267465913a182a59498b4ba292b7