diff --git a/app/exchange.py b/app/exchange.py
index 61e9afd8..9c604302 100644
--- a/app/exchange.py
+++ b/app/exchange.py
@@ -88,6 +88,13 @@ def get_historical_data(self, market_pair, exchange, time_unit, start_date=None,
                 'y': 'years'
             }
 
+            if time_period == 'M':
+                time_period = 'w'
+                time_quantity = 4
+            elif time_period == 'Y':
+                time_period = 'w'
+                time_quantity = 48
+
             timedelta_args = { timedelta_values[time_period]: int(time_quantity) }
 
             start_date_delta = timedelta(**timedelta_args)