I'm a high school student, and don't have so much time to play games, but in order to collect all the Atmas, I tried my best to buy more time spending on it.
(Except school time and doing my homework. )

more than 10 hours hard work and the result seems not so good. I just got 5 Atmas.

A Japanese player told me, the system may have a regular time to refresh, but the list he gave me didn't work well as I expected...
(GMT+9)
Atma of the MAIDEN - Central Shroud - 1:00
Atma of the SCORPION - Southern Thanalan - 2:00
Atma of the WATER BEARER - Upper La Noscea - 3:00
Atma of the GOAT - East Shroud - 4:00
Atma of the BULL - Eastern Thanalan - 5:00
Atma of the RAM - Middle La Noscea - 6:00
Atma of the TWINS - Western Thanalan - 7:00
Atma of the LION - Outer La Noscea - 8:00
Atma of the FISH - Lower La Noscea - 9:00
Atma of the ARCHER - North Shroud - 10:00
Atma of the SCALES - Central Thanalan - 11:00
Atma of the CRAB - Western La Noscea - 12:00