migration: add notes for 3.2.0

source/db-maintenance.rst

+.. _database-maintenance:
+
 Database Maintenance
 ====================
 

source/migration.rst

@@ -9,6 +9,17 @@
 The version specific instructions, unless told otherwise, must be applied even
 if a migration goes from a former version to a later version.
 
+To 3.2.0
+~~~~~~~~
+
+In this version we store only UTC dates in the database. The migration will
+convert most of the dates already stored. On a big database it can take a
+while, up to hours if there are several millions process with their logs and
+envelopes.
+
+To speedup things we recommand to use the 'purge' commands (see
+:ref:`database-maintenance`) before migrating.
+
 To 3.0.0-rc5
 ~~~~~~~~~~~~