The “day” in this game is fixed at 05:00 JST (Japan Standard Time), regardless of country or region.
The date and time displayed in in-game announcements are also all set to JST.
(Reference) Time in the following countries and regions at 05:00 JST
East Coast of the U.S. 16:00 (previous day) *Daylight saving time is +1 hour.
Central U.S. 14:00 (previous day) *+1 hour during daylight saving time
U.S. West Coast 13:00 (day before) *+1 hour during daylight saving time
Hong Kong 04:00
Taiwan 04:00
Thailand 03:00
Vietnam 03:00
Singapore 04:00
Indonesia 03:00
France 22:00 (day before) *+1 hour during daylight saving time
Germany 21:00 (day before) *+1 hour during daylight saving time
Italy 21:00 (the day before) *1 hour during daylight saving time
United Kingdom 20:00 (day before) *1 hour ahead of daylight saving time
Eastern Australia 06:00 *without daylight saving time
Central Australia 05:30 (without daylight saving time)
Western Australia 04:00