Here is the time frame and its on the Lodestone home page:

[Date & Time]
From 11:00 p.m. on Sep. 2, 2013 to 2:00 a.m. on Sep. 3, 2013 (PDT)

* The completion time may be subject to change.

[Affected Worlds]
Japan Data Center Worlds
- Aegis
- Alexander
- Anima
- Atomos
- Bahamut
- Carbuncle
- Chocobo
- Durandal
- Fenrir
- Garuda
- Gungnir
- Hades
- Ifrit
- Ixion
- Kujata
- Mandragora
- Masamune
- Ramuh
- Ridill
- Tiamat
- Titan
- Tonberry
- Typhon
- Ultima
- Valefor