From 8ba3a7fa0d99b73f7f43c1aed82c571b941eecea Mon Sep 17 00:00:00 2001
From: Mahmoud Hashemi <mahmoud@hatnote.com>
Date: Wed, 7 Dec 2022 18:22:36 -0800
Subject: [PATCH] test and fix year step and december handling in date_range,
 fixes #319

---
 boltons/timeutils.py    | 10 ++++++----
 tests/test_timeutils.py | 14 ++++++++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/boltons/timeutils.py b/boltons/timeutils.py
index 8d360d0..1ec31dd 100644
--- a/boltons/timeutils.py
+++ b/boltons/timeutils.py
@@ -377,6 +377,8 @@ def daterange(start, stop, step=1, inclusive=False):
     else:
         raise ValueError('step expected int, timedelta, or tuple'
                          ' (year, month, day), not: %r' % step)
+    
+    m_step += y_step * 12
 
     if stop is None:
         finished = lambda now, stop: False
@@ -388,10 +390,10 @@ def daterange(start, stop, step=1, inclusive=False):
 
     while not finished(now, stop):
         yield now
-        if y_step or m_step:
-            m_y_step, cur_month = divmod(now.month + m_step, 12)
-            now = now.replace(year=now.year + y_step + m_y_step,
-                              month=cur_month or 12)
+        if m_step:
+            m_y_step, cur_month = divmod((now.month - 1) + m_step, 12)
+            now = now.replace(year=now.year + m_y_step,
+                              month=(cur_month + 1))
         now = now + d_step
     return
 
diff --git a/tests/test_timeutils.py b/tests/test_timeutils.py
index 3e91ce6..631435e 100644
--- a/tests/test_timeutils.py
+++ b/tests/test_timeutils.py
@@ -48,6 +48,20 @@ def test_daterange_years():
     assert years_from_2025[0] == date(2025, 1, 1)
     assert years_from_2025[-1] == date(2017, 1, 1)
 
+
+def test_daterange_years_step():
+    start_day = date(year=2012, month=12, day=25)
+    end_day = date(year=2016, month=1, day=1)
+    dates = list(daterange(start_day, end_day, step=(1, 0, 0), inclusive=False))
+    expected = [date(year=2012, month=12, day=25), date(year=2013, month=12, day=25), date(year=2014, month=12, day=25), date(year=2015, month=12, day=25)]
+
+    assert dates == expected
+
+    dates = list(daterange(start_day, end_day, step=(0, 13, 0), inclusive=False))
+    expected = [date(year=2012, month=12, day=25), date(year=2014, month=1, day=25), date(year=2015, month=2, day=25)]
+    assert dates == expected
+
+
 def test_daterange_infinite():
     today = date.today()
     infinite_dates = daterange(today, None)