diff --git a/pycounter/helpers.py b/pycounter/helpers.py
index cea04a2..fbb4f53 100644
--- a/pycounter/helpers.py
+++ b/pycounter/helpers.py
@@ -3,6 +3,7 @@
 import datetime
 import re
 
+import pendulum
 import six
 
 
@@ -49,14 +50,7 @@ def convert_date_run(datestring):
     if isinstance(datestring, datetime.date):
         return datestring
 
-    try:
-        return datetime.datetime.strptime(datestring, "%Y-%m-%d").date()
-    except ValueError:
-        try:
-            return datetime.datetime.strptime(datestring, "%m/%d/%Y").date()
-        except ValueError:
-            # ISO 8601 without timezone
-            return datetime.datetime.strptime(datestring, "%Y-%m-%dT%H:%M:%S").date()
+    return pendulum.parse(datestring, strict=False).date()
 
 
 def convert_date_column(datestring):
diff --git a/pycounter/test/test_helpers.py b/pycounter/test/test_helpers.py
index 9221911..e6457da 100644
--- a/pycounter/test/test_helpers.py
+++ b/pycounter/test/test_helpers.py
@@ -6,7 +6,13 @@
 
 import pytest
 
-from pycounter.helpers import convert_covered, is_first_last, next_month, prev_month
+from pycounter.helpers import (
+    convert_covered,
+    convert_date_run,
+    is_first_last,
+    next_month,
+    prev_month,
+)
 
 
 @pytest.mark.parametrize(
@@ -58,3 +64,12 @@ def test_is_first_last(period, expected):
 def test_convert_covered(covered_line, expected):
     expected_dates = tuple(datetime.date(*val) for val in expected)
     assert convert_covered(covered_line) == expected_dates
+
+
+@pytest.mark.parametrize(
+    "date_run, expected",
+    [("2017-01-01", (2017, 1, 1)), ("2020-01-24T14:04:36Z", (2020, 1, 24))],
+)
+def test_convert_date_run(date_run, expected):
+    expected_date = datetime.date(*expected)
+    assert convert_date_run(date_run) == expected_date
diff --git a/pycounter/version.py b/pycounter/version.py
index 4e31341..aa59f5f 100644
--- a/pycounter/version.py
+++ b/pycounter/version.py
@@ -1,2 +1,2 @@
 """version information."""
-__version__ = "2.1.1"
+__version__ = "2.1.2"