diff --git a/fincal/fincal.py b/fincal/fincal.py
index d4a5ddf..2e2c922 100644
--- a/fincal/fincal.py
+++ b/fincal/fincal.py
@@ -99,7 +99,7 @@ def create_date_series(
             elif date.weekday() < 5:
                 dates.append(date)
 
-    return Series(dates, data_type="date")
+    return Series(dates, dtype="date")
 
 
 class TimeSeries(TimeSeriesCore):