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Fix slash dates silently parsing two-digit years as AD years #16

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Merged
Alox1d merged 2 commits into from
Oct 26, 2026
Merged

Fix slash dates silently parsing two-digit years as AD years #16

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db88e26
fix: reject ambiguous abbreviated slash years
Alox1d Oct 26, 2026
52c98e7
test: cover short slash years and full-year inputs
Alox1d Oct 26, 2026
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7 changes: 6 additions & 1 deletion dateparser/src/commonMain/kotlin/io/github/alox1d/dateparser/internal/EnglishGrammar.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -127,7 +127,12 @@ internal object EnglishGrammar {
first == second && first in 1..12 -> DateOrder.DMY
else -> null
}
when (order) {
// An abbreviated year such as 26 must not silently become AD 26.
val explicitYear = if (order == DateOrder.YMD) m.groupValues[1] else third
if (explicitYear.isNotEmpty() && explicitYear.length != 4) {
rejected = true
REJECTED
} else when (order) {
DateOrder.DMY -> date(m.groupValues[1], second, third)
DateOrder.MDY -> date(m.groupValues[2], first, third)
DateOrder.YMD -> if (third.isEmpty()) { rejected = true; REJECTED } else date(third, second, m.groupValues[1])
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12 changes: 12 additions & 0 deletions dateparser/src/commonTest/kotlin/io/github/alox1d/dateparser/EnglishGrammarTest.kt
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Expand Up @@ -39,6 +39,18 @@ class EnglishGrammarTest {
assertTrue(parse("03/04").isEmpty())
assertEquals(LocalDate(2026,4,3), parse("03.04.2026",DateOrder.MDY).single().targetDate.date)
}
@Test fun shortSlashYearsCannotSilentlyBecomeAncientDates() {
val parser = DateParser()
for (text in listOf("13/04/26", "04/13/26")) {
assertTrue(parser.parse(text, reference, TimeZone.UTC).isEmpty(), text)
}
assertTrue(parser.parse("13/04/26", DateOrder.DMY, reference, TimeZone.UTC).isEmpty())
assertTrue(parser.parse("04/13/26", DateOrder.MDY, reference, TimeZone.UTC).isEmpty())
assertTrue(parser.parse("26/04/13", DateOrder.YMD, reference, TimeZone.UTC).isEmpty())
assertEquals(LocalDate(2026, 4, 13), parser.parse("13/04/2026", reference, TimeZone.UTC).single().targetDate.date)
assertEquals(LocalDate(2026, 4, 13), parser.parse("2026/04/13", DateOrder.YMD, reference, TimeZone.UTC).single().targetDate.date)
assertEquals(LocalDate(2024, 4, 13), parser.parse("13/04", reference, TimeZone.UTC).single().targetDate.date)
}
@Test fun invalidDateAndClockTokensNeverBecomePartialMatches() {
for (text in listOf("February 30, 2026", "29 February 2025", "31 April", "February 29, 0000", "13pm", "0AM", "5:60PM", "12:10:60am", "2026-02-30", "31/04/2026", "03/04/2026 at 5pm", "tomorrow at 13pm", "tomorrow at 1:2:3:4pm", "March 12, 10000", "tomorrow at 999999999999999999999pm", "01/02/03/04", "2026-02-29")) {
assertTrue(parse(text).isEmpty(), text)
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