In order to get this achievement, you must
complete the game while the moon is in full state in the real world.
There are a few moments where you see the moon in game, and it reflects the current state of the moon, for example, this image is what the game shows as I am writing this:
Said moments are: the main menu of the game (thanks,
Ackter), the opening cinematic, the crack in the wall required for "The Shadow Of Doubt" achievement and the ending cinematic. For this achievement, you have to
watch the ending cinematic while the moon is full.
So, you can do the achievement in two ways.
-
Use a lunar calendar (like this one:
http://stardate.org/nightsky/moon ) and complete the final chapter on a day of full moon.
-
Disconnect your console from the internet and set your date and time to a day of full moon. For example, use
March 5th, 2015, 00:15h. Complete the game while offline, and then reconnect. Wait a few minutes and the achievement will pop. Also, if you have all the other collectibles at the moment of finishing the game (except for one Boston Daily entry that requires finishing the game in a full moon day), you'll get the following achievements.
The Around the clock achievement in White Night worth 149 pointsFinish the game on a full Moon day, read all the books and the articles from the Boston Daily News The Archivist achievement in White Night worth 148 pointsUnlock all newspaper articles from the Boston Daily News NOTE: If your console doesn't let you change time and date, you have to turn the console completely off (by holding power button for around ten seconds) and then turning it on while offline (ethernet cable must be disconnected, or if you automatically connect via wifi, you'll need to delete the wifi connection that you use, before restarting). When turning the console on while offline, it should let you change date and time.