Fix international letter rate start dates

These were not taking timezones into account before.

migrations/versions/0325_int_letter_rates_fix.py

@@ -0,0 +1,32 @@
+"""
+
+Revision ID: 0325_int_letter_rates_fix
+Revises: 0324_int_letter_rates
+Create Date: 2020-07-15 10:09:17.218183
+
+"""
+from datetime import datetime
+
+from alembic import op
+from sqlalchemy.sql import text
+
+revision = '0325_int_letter_rates_fix'
+down_revision = '0324_int_letter_rates'
+
+
+old_start_date = datetime(2020, 7, 1, 0, 0)
+new_start_date = datetime(2020, 6, 30, 23, 0)
+
+
+def upgrade():
+    conn = op.get_bind()
+    conn.execute(text(
+        """UPDATE letter_rates SET start_date = :new_start_date WHERE start_date = :old_start_date"""
+    ), new_start_date=new_start_date, old_start_date=old_start_date)
+
+
+def downgrade():
+    conn = op.get_bind()
+    conn.execute(text(
+        """UPDATE letter_rates SET start_date = :old_start_date WHERE start_date = :new_start_date"""
+    ), old_start_date=old_start_date, new_start_date=new_start_date)