Change get_financial_year to return ending date as 1 microsecond earlier.

That way we can write the queries as between start and end dates, making it easier to read.
This makes more sense.

app/dao/date_util.py

@@ -1,10 +1,10 @@
-from datetime import datetime
+from datetime import datetime, timedelta
 
 import pytz
 
 
 def get_financial_year(year):
-    return get_april_fools(year), get_april_fools(year + 1)
+    return get_april_fools(year), get_april_fools(year + 1) - timedelta(microseconds=1)
 
 
 def get_april_fools(year):

app/dao/notification_usage_dao.py

@@ -1,7 +1,7 @@
 from datetime import datetime
 
 from sqlalchemy import Float, Integer
-from sqlalchemy import func, case, cast, desc, between
+from sqlalchemy import func, case, cast
 from sqlalchemy import literal_column
 
 from app import db
@@ -49,8 +49,7 @@ def get_monthly_billing_data(service_id, year):
 def billing_data_filter(notification_type, start_date, end_date, service_id):
     return [
         NotificationHistory.notification_type == notification_type,
-        NotificationHistory.created_at >= start_date,
-        NotificationHistory.created_at < end_date,
+        NotificationHistory.created_at.between(start_date, end_date),
         NotificationHistory.service_id == service_id,
         NotificationHistory.status.in_(NOTIFICATION_STATUS_TYPES_BILLABLE),
         NotificationHistory.key_type != KEY_TYPE_TEST
@@ -106,11 +105,11 @@ def get_rates_for_year(start_date, end_date, notification_type):
     rates = Rate.query.filter(Rate.notification_type == notification_type).order_by(Rate.valid_from).all()
     results = []
     for current_rate, current_rate_expiry_date in zip(rates, rates[1:]):
-        if is_between_end_date_exclusive(current_rate.valid_from, start_date, end_date) or \
-                is_between_end_date_exclusive(current_rate_expiry_date.valid_from, start_date, end_date):
+        if is_between(current_rate.valid_from, start_date, end_date) or \
+                is_between(current_rate_expiry_date.valid_from, start_date, end_date):
             results.append(current_rate)
 
-    if is_between_end_date_exclusive(rates[-1].valid_from, start_date, end_date):
+    if is_between(rates[-1].valid_from, start_date, end_date):
         results.append(rates[-1])
 
     if not results:
@@ -120,8 +119,8 @@ def get_rates_for_year(start_date, end_date, notification_type):
     return results
 
 
-def is_between_end_date_exclusive(date, start_date, end_date):
-    return start_date <= date < end_date
+def is_between(date, start_date, end_date):
+    return start_date <= date <= end_date
 
 
 def sms_billing_data_per_month_query(rate, service_id, start_date, end_date):

app/dao/notifications_dao.py

@@ -250,8 +250,7 @@ def get_notification_billable_unit_count_per_month(service_id, year):
     ).filter(
         NotificationHistory.billable_units != 0,
         NotificationHistory.service_id == service_id,
-        NotificationHistory.created_at >= start_date,
-        NotificationHistory.created_at < end_date
+        NotificationHistory.created_at.between(start_date, end_date)
     ).group_by(
         month
     ).order_by(

app/dao/services_dao.py

@@ -237,8 +237,7 @@ def dao_fetch_monthly_historical_stats_by_template_for_service(service_id, year)
         func.count().label('count')
     ).filter(
         NotificationHistory.service_id == service_id,
-        NotificationHistory.created_at >= start_date,
-        NotificationHistory.created_at < end_date
+        NotificationHistory.created_at.between(start_date, end_date)
 
     ).group_by(
         month,
@@ -273,8 +272,7 @@ def dao_fetch_monthly_historical_stats_for_service(service_id, year):
         func.count(NotificationHistory.id).label('count')
     ).filter(
         NotificationHistory.service_id == service_id,
-        NotificationHistory.created_at >= start_date,
-        NotificationHistory.created_at < end_date
+        NotificationHistory.created_at.between(start_date, end_date)
     ).group_by(
         NotificationHistory.notification_type,
         NotificationHistory.status,