bold textTo start with, almost all of the comments in the Japanese diary post are people who have tested the method and can confirm that it is indeed working. Many of them have been farming for days without luck and have obtained multiple Atma within hours of trying this.

Just to help out with the translation a bit:
The idea is that all Atma have specific drop times, indicated by the list below:

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

AM/PM is irrelevant. The time appears to be local time, not server or Eorzea time.

The drop rate appears to be high enough at the indicated times that most people got their drop within 10-15 minutes (3-4 FATES).

Of course, the best way to find out if this works is to try it yourself.

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