From 5bf6980a7b386211d197ccd93ae061e66dc7523a Mon Sep 17 00:00:00 2001
From: Kian Cross <kian@kiancross.co.uk>
Date: Mon, 10 Feb 2025 10:33:14 +0000
Subject: [PATCH] Improve date format heuristic for bank statement import
 (#4814)

When dates are ambiguous, use the event's locale to infer whether the
day or month comes first. Since regions follow certain date format
conventions, this helps make more accurate guesses.
---
 src/pretix/plugins/banktransfer/tasks.py      |  6 ++--
 src/tests/plugins/banktransfer/test_import.py | 30 +++++++++++++++++++
 .../plugins/banktransfer/test_parsing.py      |  2 ++
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/pretix/plugins/banktransfer/tasks.py b/src/pretix/plugins/banktransfer/tasks.py
index 174ff437e3..301f799e2a 100644
--- a/src/pretix/plugins/banktransfer/tasks.py
+++ b/src/pretix/plugins/banktransfer/tasks.py
@@ -292,11 +292,11 @@ def _handle_transaction(trans: BankTransaction, matches: tuple, event: Event = N
     trans.save()
 
 
-def parse_date(date_str):
+def parse_date(date_str, region=None):
     try:
         return dateutil.parser.parse(
             date_str,
-            dayfirst="." in date_str,
+            dayfirst="." in date_str or region in ["GB"],
         ).date()
     except (ValueError, OverflowError):
         pass
@@ -339,7 +339,7 @@ def _get_unknown_transactions(job: BankImportJob, data: list, event: Event = Non
                                 external_id=row.get('external_id'),
                                 currency=event.currency if event else job.currency)
 
-        trans.date_parsed = parse_date(trans.date)
+        trans.date_parsed = parse_date(trans.date, (event and event.settings.region) or (organizer and organizer.settings.region) or None)
 
         trans.checksum = trans.calculate_checksum()
         if trans.checksum not in known_checksums and (not trans.external_id or (trans.external_id, trans.date, trans.amount) not in known_by_external_id):
diff --git a/src/tests/plugins/banktransfer/test_import.py b/src/tests/plugins/banktransfer/test_import.py
index 49a7f8db37..e438322405 100644
--- a/src/tests/plugins/banktransfer/test_import.py
+++ b/src/tests/plugins/banktransfer/test_import.py
@@ -790,3 +790,33 @@ def test_ignore_by_external_id(env, job):
     }])
     with scopes_disabled():
         assert BankTransaction.objects.count() == 2
+
+
+@pytest.mark.django_db
+def test_ambigious_date_without_region(env, job):
+    process_banktransfers(job, [{
+        'payer': 'Karla Kundin',
+        'reference': 'Bestellung DUMMY1Z3AS',
+        'date': '03/05/2016',
+        'amount': '23.00'
+    }])
+    env[2].refresh_from_db()
+
+    with scopes_disabled():
+        assert env[2].payments.last().info_data["date"] == "2016-03-05"
+
+
+@pytest.mark.django_db
+def test_ambigious_date_with_region(env, job):
+    env[0].settings.region = "GB"
+
+    process_banktransfers(job, [{
+        'payer': 'Karla Kundin',
+        'reference': 'Bestellung DUMMY1Z3AS',
+        'date': '03/05/2016',
+        'amount': '23.00'
+    }])
+    env[2].refresh_from_db()
+
+    with scopes_disabled():
+        assert env[2].payments.last().info_data["date"] == "2016-05-03"
diff --git a/src/tests/plugins/banktransfer/test_parsing.py b/src/tests/plugins/banktransfer/test_parsing.py
index 3c6e73a9fb..e338c3c6dc 100644
--- a/src/tests/plugins/banktransfer/test_parsing.py
+++ b/src/tests/plugins/banktransfer/test_parsing.py
@@ -40,3 +40,5 @@ def test_date_formats():
 
     assert dt == parse_date("2020-07-01")
     assert dt == parse_date("2020-7-1")
+
+    assert dt == parse_date("01/07/2020", "GB")