DOC: added a more generic behavior statement as suggested. pandas-dev#33399

Author: venkateshdatta-miq

pandas/core/generic.py

@@ -5549,7 +5549,8 @@ def astype(
         dtype: datetime64[ns]
 
         Convert to datetime type with time zone
-        (Behavior - Localize to UTC and convert to US/Eastern):
+        (Behavior - Datetimes are localized to UTC first
+        before converting to the specified timezone):
 
         >>> ser_date.astype('datetime64[ns, US/Eastern]')
         0   2019-12-31 19:00:00-05:00