diff --git a/fincal/fincal.py b/fincal/fincal.py
index c060383..fcb8554 100644
--- a/fincal/fincal.py
+++ b/fincal/fincal.py
@@ -234,7 +234,7 @@ class TimeSeries:
         self,
         from_date: datetime.date,
         to_date: datetime.date,
-        frequency: str = "d",
+        frequency: str = "D",
         closest: str = "previous",
         compounding: bool = True,
         years: int = 1,