There are 2 maintenances happening.

First, is the EU Data Centre maintenance which is occurring between:
[Date & Time]
Apr. 1, 2019 10:00 to Apr. 2, 2019 10:00 (GMT)
Apr. 1, 2019 11:00 to Apr. 2, 2019 11:00 (BST)
* Completion time is subject to change.

Second is the All Worlds maintenance which is occurring between:
[Date & Time]
Apr. 2, 2019 4:00 to 10:00 (GMT)
Apr. 2, 2019 5:00 to 11:00 (BST)
* Completion time is subject to change.

I can see where the confusion is coming from, because, until today, the client didn't list the EU Data Centre maintenance and only showed the All Worlds maintenance with merely a topic about "Important information regarding the expansion of the European Data Centre" which stated the timing of the free transfers because of the change (From Tuesday, 2 April, 2019 (after maintenance) through Wednesday, 17 April, at 3:00 (GMT) / 4:00 (BST))