diff --git a/pvlib/iotools/bsrn.py b/pvlib/iotools/bsrn.py
index 3cca48c959..7830853826 100644
--- a/pvlib/iotools/bsrn.py
+++ b/pvlib/iotools/bsrn.py
@@ -162,8 +162,7 @@ def get_bsrn(station, start, end, username, password,
     end = pd.to_datetime(end)
 
     # Generate list files to download based on start/end (SSSMMYY.dat.gz)
-    filenames = pd.date_range(
-        start, end.replace(day=1) + pd.DateOffset(months=1), freq='1M')\
+    filenames = pd.date_range(start.date().replace(day=1), end, freq='1MS')\
         .strftime(f"{station}%m%y.dat.gz").tolist()
 
     # Create FTP connection
diff --git a/pvlib/iotools/srml.py b/pvlib/iotools/srml.py
index 728c3a7093..c9b630ec6e 100644
--- a/pvlib/iotools/srml.py
+++ b/pvlib/iotools/srml.py
@@ -236,8 +236,7 @@ def get_srml(station, start, end, filetype='PO', map_variables=True,
     end = pd.to_datetime(end)
 
     # Generate list of months
-    months = pd.date_range(
-        start, end.replace(day=1) + pd.DateOffset(months=1), freq='1M')
+    months = pd.date_range(start.date().replace(day=1), end, freq='1MS')
     months_str = months.strftime('%y%m')
 
     # Generate list of filenames
diff --git a/tests/test_clearsky.py b/tests/test_clearsky.py
index ef943ac39d..0ef5dfeacd 100644
--- a/tests/test_clearsky.py
+++ b/tests/test_clearsky.py
@@ -224,8 +224,9 @@ def test_lookup_linke_turbidity_nointerp():
 
 
 def test_lookup_linke_turbidity_months():
-    times = pd.date_range(start='2014-04-01', end='2014-07-01',
-                          freq='1M', tz='America/Phoenix')
+    times = pd.date_range(start='2014-05-01', end='2014-07-01',
+                          freq='1MS', tz='America/Phoenix',
+                          ) - pd.Timedelta(days=1)
     expected = pd.Series(
         np.array([2.89918032787, 2.97540983607, 3.19672131148]), index=times
     )
@@ -234,8 +235,9 @@ def test_lookup_linke_turbidity_months():
 
 
 def test_lookup_linke_turbidity_months_leapyear():
-    times = pd.date_range(start='2016-04-01', end='2016-07-01',
-                          freq='1M', tz='America/Phoenix')
+    times = pd.date_range(start='2016-05-01', end='2016-07-01',
+                          freq='1MS', tz='America/Phoenix',
+                          ) - pd.Timedelta(days=1)
     expected = pd.Series(
         np.array([2.89918032787, 2.97540983607, 3.19672131148]), index=times
     )
@@ -245,14 +247,16 @@ def test_lookup_linke_turbidity_months_leapyear():
 
 def test_lookup_linke_turbidity_nointerp_months():
     times = pd.date_range(start='2014-04-10', end='2014-07-10',
-                          freq='1M', tz='America/Phoenix')
+                          freq='1MS', tz='America/Phoenix',
+                          ) - pd.Timedelta(days=1)
     expected = pd.Series(np.array([2.85, 2.95, 3.]), index=times)
     out = clearsky.lookup_linke_turbidity(times, 32.125, -110.875,
                                           interp_turbidity=False)
     assert_series_equal(expected, out)
     # changing the dates shouldn't matter if interp=False
     times = pd.date_range(start='2014-04-05', end='2014-07-05',
-                          freq='1M', tz='America/Phoenix')
+                          freq='1MS', tz='America/Phoenix',
+                          ) - pd.Timedelta(days=1)
     out = clearsky.lookup_linke_turbidity(times, 32.125, -110.875,
                                           interp_turbidity=False)
     assert_series_equal(expected, out)