diff --git a/fincal/utils.py b/fincal/utils.py
index dc2584c..7014535 100644
--- a/fincal/utils.py
+++ b/fincal/utils.py
@@ -116,7 +116,7 @@ def _find_closest_date(
     raise ValueError(f"Invalid argument for if_not_found: {if_not_found}")
 
 
-def _interval_to_years(interval_type: Literal["years", "months", "day"], interval_value: int) -> int:
+def _interval_to_years(interval_type: Literal["years", "months", "day"], interval_value: int) -> float:
     """Converts any time period to years for use with compounding functions"""
 
     year_conversion_factor = {"years": 1, "months": 12, "days": 365}
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 0000000..ed575f5
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,26 @@
+import datetime
+
+import pytest
+from fincal.utils import _interval_to_years, _parse_date
+
+
+class TestParseDate:
+    def test_parsing(self):
+        dt = datetime.datetime(2020, 1, 1)
+        assert _parse_date(dt) == dt
+        assert _parse_date(dt.strftime("%Y-%m-%d")) == dt
+        assert _parse_date(datetime.date(2020, 1, 1)) == dt
+        assert _parse_date("01-01-2020", date_format="%d-%m-%Y") == dt
+        assert _parse_date("01-01-2020", date_format="%m-%d-%Y") == dt
+
+    def test_errors(self):
+        with pytest.raises(ValueError):
+            _parse_date("01-01-2020")
+
+        with pytest.raises(ValueError):
+            _parse_date("abcdefg")
+
+
+class TestIntervalToYears:
+    def test_months(self):
+        assert _interval_to_years("months", 6) == 0.5