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Fix %I/%-I strftime directives to use the 12-hour clock #182

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Merged
slashmili merged 2 commits into from
Aug 6, 2026
Merged

Fix %I/%-I strftime directives to use the 12-hour clock #182

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f0acee4
Fix %I/%-I strftime directives to use the 12-hour clock
gaoflow Jul 7, 2026
5ca3e11
Make hour12 property private (_hour12)
gaoflow Jul 15, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

### Fixed

* `%I` and `%-I` now render the 12-hour clock instead of duplicating `%H`
* pass Gregorian to tzinfo.dst #188
* typing: use int for fold #186

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10 changes: 8 additions & 2 deletions jdatetime/__init__.py
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Expand Up @@ -45,8 +45,8 @@
'%f': ('_strftime_get_attr_value', {'attr': 'microsecond', 'fmt': '%06.d', 'fb': '000000'}),
'%H': ('_strftime_get_attr_value', {'attr': 'hour', 'fmt': '%02.d', 'fb': '00'}),
'%-H': ('_strftime_get_attr_value', {'attr': 'hour', 'fmt': '%d', 'fb': '0'}),
'%I': ('_strftime_get_attr_value', {'attr': 'hour', 'fmt': '%02.d', 'fb': '12'}),
'%-I': ('_strftime_get_attr_value', {'attr': 'hour', 'fmt': '%d', 'fb': '12'}),
'%I': ('_strftime_get_attr_value', {'attr': '_hour12', 'fmt': '%02.d', 'fb': '12'}),
'%-I': ('_strftime_get_attr_value', {'attr': '_hour12', 'fmt': '%d', 'fb': '12'}),
'%M': ('_strftime_get_attr_value', {'attr': 'minute', 'fmt': '%02.d', 'fb': '00'}),
'%-M': ('_strftime_get_attr_value', {'attr': 'minute', 'fmt': '%d', 'fb': '0'}),
'%S': ('_strftime_get_attr_value', {'attr': 'second', 'fmt': '%02.d', 'fb': '00'}),
Expand Down Expand Up @@ -871,6 +871,12 @@ def fromordinal(ordinal: int) -> datetime:
def hour(self) -> int:
return self.__time.hour

@property
def _hour12(self) -> int:
"""Return the hour on a 12-hour clock (1..12), used by the %I directive."""
hour = self.hour % 12
return 12 if hour == 0 else hour

@property
def minute(self) -> int:
return self.__time.minute
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25 changes: 25 additions & 0 deletions tests/test_jdatetime.py
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Expand Up @@ -211,6 +211,31 @@ def dst(self, dt):
dt = jdatetime.datetime(1389, 2, 17, 19, 10, 2, tzinfo=teh)
self.assertEqual(dt.strftime('%Z %z'), 'IRDT +0330')

def test_strftime_I_directive_uses_twelve_hour_clock(self):
import datetime as _std

# %I and %-I must render the 12-hour clock (1..12), matching stdlib.
for hour in range(24):
with self.subTest(hour=hour):
jd = jdatetime.datetime(1400, 1, 1, hour, 5, 0)
std = _std.datetime(2020, 1, 1, hour, 5, 0)
self.assertEqual(jd.strftime('%I'), std.strftime('%I'))
self.assertEqual(jd.strftime('%-I'), std.strftime('%-I'))

@5j9 5j9 Aug 6, 2026

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%-I (a GNU extension for %I) is not supported by the standard datetime module on Windows, which causes the std.strftime('%-I') comparison to fail in Windows test runs.

self.assertEqual(jd._hour12, int(std.strftime('%I')))
# %I must be consistent with the (correct) %p directive:
# reconstructing the 24-hour value from (%p, %I) round-trips.
twelve = int(jd.strftime('%I'))
base = 0 if twelve == 12 else twelve
reconstructed = base + (12 if jd.strftime('%p') == 'PM' else 0)
self.assertEqual(reconstructed, hour)
# Spot-check the values that the previous 24-hour behaviour got wrong.
self.assertEqual(jdatetime.datetime(1400, 1, 1, 0, 0).strftime('%I'), '12')
self.assertEqual(jdatetime.datetime(1400, 1, 1, 13, 0).strftime('%I'), '01')
self.assertEqual(jdatetime.datetime(1400, 1, 1, 23, 0).strftime('%I'), '11')
self.assertEqual(jdatetime.datetime(1400, 1, 1, 13, 0).strftime('%-I'), '1')
# A plain date (no time component) is midnight -> 12.
self.assertEqual(jdatetime.date(1400, 1, 1).strftime('%I'), '12')

def test_strftime_fa_locale_uses_short_month_names_for_b_directive(self):
tests = [
(1, 'فرو', 'فروردین'),
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