From b4934c91b557349615e119535ec55cb662c2189c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C5=8Dan?= <koan.bot@atoomic.org>
Date: Sun, 3 May 2026 06:21:05 -0600
Subject: [PATCH] fix: DD-MM-YYYY swap off-by-one for day 13
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The date swap logic uses 0-indexed months ($month = $1 - 1) but
checked $month > 12 instead of $month > 11. This meant that when the
first field was exactly 13, $month was 12 (one past December), which
did NOT trigger the swap — so "13-01-2025" was parsed as invalid
month 12 instead of January 13.

Fix: change the boundary check from $month > 12 to $month > 11, so
any value that cannot be a valid month (0-11) triggers the DD-MM-YYYY
or YYYY-MM-DD disambiguation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 lib/Date/Parse.pm |  2 +-
 t/ddmmyyyy.t      | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/Date/Parse.pm b/lib/Date/Parse.pm
index fd6cef2..0a2f614 100644
--- a/lib/Date/Parse.pm
+++ b/lib/Date/Parse.pm
@@ -162,7 +162,7 @@ sub {
       if ($5) {
     $year = $5;
     # Possible match for 1995-01-24 or 31-12-2023
-    if ($month > 12) {
+    if ($month > 11) {
       if ($1 > 31) {
         # YYYY-MM-DD (mainframe date format)
         ($year,$month,$day) = ($1, $3 - 1, $5);
diff --git a/t/ddmmyyyy.t b/t/ddmmyyyy.t
index 726019c..f778407 100644
--- a/t/ddmmyyyy.t
+++ b/t/ddmmyyyy.t
@@ -1,6 +1,6 @@
 use strict;
 use warnings;
-use Test::More tests => 12;
+use Test::More tests => 18;
 use Date::Parse qw(strptime str2time);
 
 # DD-MM-YYYY (European date format) — the first field exceeds 12,
@@ -33,3 +33,18 @@ is($r[4], 11, "31-12-96: month = 11 (December, 0-based)");
 is($r[3], 24, "1995-01-24: day = 24");
 is($r[4], 0,  "1995-01-24: month = 0 (January, 0-based)");
 is($r[5], 95, "1995-01-24: year = 95 (1995 - 1900)");
+
+# 13-01-2025 → 13 Jan 2025
+# Regression: first field = 13 produces $month = 12 (0-indexed),
+# which is > 11 but was NOT > 12 in the old check, so the swap
+# from MM-DD to DD-MM never triggered.
+@r = strptime("13-01-2025");
+is($r[3], 13, "13-01-2025: day = 13 (not treated as month)");
+is($r[4], 0,  "13-01-2025: month = 0 (January, 0-based)");
+is($r[5], 125, "13-01-2025: year = 125 (2025 - 1900)");
+ok(defined str2time("13-01-2025"), "str2time('13-01-2025') is defined");
+
+# 14-02-2025 → 14 Feb 2025 (also affected by off-by-one)
+@r = strptime("14-02-2025");
+is($r[3], 14, "14-02-2025: day = 14");
+is($r[4], 1,  "14-02-2025: month = 1 (February, 0-based)");