SEA and EU have made this announcement two days earlier than normal but I suppose it saves someone working on Sunday.

For SEA.

World of Tanks Asia periphery servers will be undergoing maintenance on 15 July, 2019 at around 11:00 UTC+8 to deploy micropatch 1.5.1_5.1. No downtime is required.

Patch Notes.

• Add new folder for mods.

For EU

The World of Tanks servers and Clan Portal will be unavailable on 15.07.2019 from 06:00 – 06:45 CEST due to this update.

But why does one region need to shut the servers down and another not ?