FA-76916 / Calendar recurrence rules / Open access
Monthly BYSETPOS selection from a weekday set: setpos before filter · case 01
In the first month BYSETPOS=1 picks the first weekday after dtstart instead of the first of the month.
ROOT CAUSE
Candidates are filtered by dtstart before positions are applied, renumbering the first month.
VERIFIED REPAIR
At the setpos before filter decision use `dt.date(y, m, 1)`, leaving the other decision sites of the model unchanged.
Unsuccessful approach: The partial repair `start + dt.timedelta(days=1)` still filters by dtstart before selection and additionally drops dtstart itself.
Case contract
FREQ=MONTHLY;BYDAY=<weekdays>;BYSETPOS=<positions>. For each month from the dtstart month, the candidate set is every day of the whole month whose weekday is listed, in date order. Positions are 1-based, negative from the end; out-of-range positions are ignored and positions naming the same day yield it once. Selected days are emitted chronologically; days before dtstart are dropped after selection. Return the first count ISO dates.
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, weekdays, setpos, count):
start = dt.date.fromisoformat(dtstart)
out = []
for k in range(240):
mi = start.month - 1 + k
y, m = start.year + mi // 12, mi % 12 + 1
dim = calendar.monthrange(y, m)[1]
cand = [x for x in [dt.date(y, m, d) for d in range(1, dim + 1)] if x.weekday() in weekdays and x >= start]
picked = []
for p in setpos:
idx = p - 1 if p > 0 else len(cand) + p
if 0 <= idx < len(cand) and cand[idx] not in picked:
picked.append(cand[idx])
for d in sorted(picked):
if d < start:
continue
out.append(d.isoformat())
if len(out) >= count:
return out
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30'])],
[('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27'])],
[('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31'])],
[('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'])],
[('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'])]]
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: last weekday of month | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | Passed |
| first weekday, dtstart mid-month | ['2024-01-10', '2024-02-01', '2024-03-01'] | ['2024-02-01', '2024-03-01', '2024-04-01'] | Failed |
| first and last in reverse order | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | Passed |
| coinciding positions | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | Passed |
| three positions with repeat | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | Passed |
| out of range negative | ['2024-01-06', '2024-01-07', '2024-02-03'] | ['2024-01-06', '2024-01-07', '2024-02-03'] | Passed |
| out of range positive | ['2024-04-29', '2024-07-29', '2024-09-30'] | ['2024-04-29', '2024-07-29', '2024-09-30'] | Passed |
SHA-256 / b09497efafdd4eaf30db965ae53839047eb0756591d90521f071c9a5ba15520f
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, weekdays, setpos, count):
start = dt.date.fromisoformat(dtstart)
out = []
for k in range(240):
mi = start.month - 1 + k
y, m = start.year + mi // 12, mi % 12 + 1
dim = calendar.monthrange(y, m)[1]
cand = [x for x in [dt.date(y, m, d) for d in range(1, dim + 1)] if x.weekday() in weekdays and x >= start + dt.timedelta(days=1)]
picked = []
for p in setpos:
idx = p - 1 if p > 0 else len(cand) + p
if 0 <= idx < len(cand) and cand[idx] not in picked:
picked.append(cand[idx])
for d in sorted(picked):
if d < start:
continue
out.append(d.isoformat())
if len(out) >= count:
return out
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30'])],
[('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27'])],
[('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31'])],
[('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'])],
[('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'])]]
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: last weekday of month | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | Passed |
| first weekday, dtstart mid-month | ['2024-01-11', '2024-02-01', '2024-03-01'] | ['2024-02-01', '2024-03-01', '2024-04-01'] | Failed |
| first and last in reverse order | ['2024-03-04', '2024-03-29', '2024-04-01', '2024-04-30'] | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | Failed |
| coinciding positions | ['2024-01-08', '2024-02-05', '2024-03-04', '2024-04-01'] | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | Failed |
| three positions with repeat | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | Passed |
| out of range negative | ['2024-01-06', '2024-01-07', '2024-02-03'] | ['2024-01-06', '2024-01-07', '2024-02-03'] | Passed |
| out of range positive | ['2024-04-29', '2024-07-29', '2024-09-30'] | ['2024-04-29', '2024-07-29', '2024-09-30'] | Passed |
SHA-256 / 2f4eb76cdab8a4a8e40e37fe5e00aee3e2ca7e60531ad5758302964c6c5ea360
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, weekdays, setpos, count):
start = dt.date.fromisoformat(dtstart)
out = []
for k in range(240):
mi = start.month - 1 + k
y, m = start.year + mi // 12, mi % 12 + 1
dim = calendar.monthrange(y, m)[1]
cand = [x for x in [dt.date(y, m, d) for d in range(1, dim + 1)] if x.weekday() in weekdays and x >= dt.date(y, m, 1)]
picked = []
for p in setpos:
idx = p - 1 if p > 0 else len(cand) + p
if 0 <= idx < len(cand) and cand[idx] not in picked:
picked.append(cand[idx])
for d in sorted(picked):
if d < start:
continue
out.append(d.isoformat())
if len(out) >= count:
return out
return out
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30'])],
[('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30']),
('coinciding positions',
['2024-01-01', [0], [1, -5], 4],
['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01']),
('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27'])],
[('three positions with repeat',
['2024-04-01', [2], [1, -1, -5], 5],
['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05']),
('out of range negative', ['2024-01-01', [5, 6], [-7, 1], 3], ['2024-01-06', '2024-01-07', '2024-02-03']),
('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31'])],
[('out of range positive', ['2024-02-01', [0], [5], 3], ['2024-04-29', '2024-07-29', '2024-09-30']),
('second weekend day', ['2024-06-15', [5, 6], [2], 3], ['2024-07-07', '2024-08-04', '2024-09-07']),
('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'])],
[('second to last weekday',
['2024-07-01', [0, 1, 2, 3, 4], [-2], 3],
['2024-07-30', '2024-08-29', '2024-09-27']),
('position 3 of TU,TH mid month',
['2024-09-12', [1, 3], [3, -1], 4],
['2024-09-26', '2024-10-08', '2024-10-31', '2024-11-12']),
('december rollover',
['2024-12-01', [4], [1, -1], 4],
['2024-12-06', '2024-12-27', '2025-01-03', '2025-01-31']),
('dtstart equals picked day', ['2024-05-31', [0, 1, 2, 3, 4], [-1], 2], ['2024-05-31', '2024-06-28']),
('regression: last weekday of month',
['2024-01-01', [0, 1, 2, 3, 4], [-1], 4],
['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30']),
('first weekday, dtstart mid-month',
['2024-01-10', [0, 1, 2, 3, 4], [1], 3],
['2024-02-01', '2024-03-01', '2024-04-01']),
('first and last in reverse order',
['2024-03-01', [0, 1, 2, 3, 4], [-1, 1], 4],
['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'])]]
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: last weekday of month | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | ['2024-01-31', '2024-02-29', '2024-03-29', '2024-04-30'] | Passed |
| first weekday, dtstart mid-month | ['2024-02-01', '2024-03-01', '2024-04-01'] | ['2024-02-01', '2024-03-01', '2024-04-01'] | Passed |
| first and last in reverse order | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | ['2024-03-01', '2024-03-29', '2024-04-01', '2024-04-30'] | Passed |
| coinciding positions | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | ['2024-01-01', '2024-02-05', '2024-03-04', '2024-04-01'] | Passed |
| three positions with repeat | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | ['2024-04-03', '2024-04-24', '2024-05-01', '2024-05-29', '2024-06-05'] | Passed |
| out of range negative | ['2024-01-06', '2024-01-07', '2024-02-03'] | ['2024-01-06', '2024-01-07', '2024-02-03'] | Passed |
| out of range positive | ['2024-04-29', '2024-07-29', '2024-09-30'] | ['2024-04-29', '2024-07-29', '2024-09-30'] | Passed |
SHA-256 / 5cd33953623a1ca77e6e3d750f8cf4005eb074d89f06d905debd5cb2e0b42709
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 2026-09-29T14:49:20.635145+00:00.
Case digest / b03d70468698883182dae96399b9e0fc97cc37dc95a5b512c9474fe7fd909ef2