There are several special days that can have significant effects on gameplay. Some of these are linked to the in-world Ancardian calendar, others are linked to specific real-world calendar days.
Ancardian Calendar Days
These are the days that have significant effects on the in-game clock. The date can be adjusted simply by waiting for extended periods of time.
Darknight is the first day of every month, and, as it happens, is the day that the PC's adventure will always begin. On this day, casting costs for chaotic PCs are reduced (seemingly except for the Wish spell). In addition, chaotic spellcasting monsters are increased in power: their energy bolts and other spells do more damage, and their confusion, stat drains, and item cursing are more likely to succeed. The Ancient Stone Circle is only accessible at midnight on Darknight, provided that the PC has satisfied the demented ratling.
Silvernight occurs on day 16 of each month. On this day, casting costs for lawful PCs are reduced, and casting costs for chaotic PCs are increased. In addition, chaotic spellcasting monsters are reduced in power: their energy bolts and other spells do less damage, and their confusion, stat drains, and item cursing are less likely to succeed.
The character's birthday is assigned at character creation based on their starsign. When the PC's birthday happens, the message "Happy birthday!" will appear. PCs will receive a substantial bonus to their luck score on their birthday. Unfortunately, they do not receive any presents.
Real-world Calendar Days
These are days that have significant effects on gameplay based on the real-world calendar.
Creator's day is July 2, the birthday of ADOM creator Thomas Biskup. PCs generated on this day will start with the Lucky and Fate Smiles intrinsics. The message "You feel that starting your adventure on Creator's Day was a good idea." is generated.
Characters generated on December 24 will receive the Fate Smiles intrinsic at the start of the game. The message "A lone star leads you to this remote valley." is generated.
New Year's Eve
Characters generated on December 31 will start the game with 6 extra blessed potions of booze. The message "You feel well prepared for the coming year." is generated.
A special day was added in 1.2.0 to mark the success of the campaign to resurrect ADOM development and thus make the development of 1.2.0 possible.
All characters generated on August 22 start with the Boon to the Family talent. Consequently, as well as having extra starting money, such characters only need two available starting talents to be eligible for the Heir talent.
An additional day was added in 1.2.0 to mark the end of the aforementioned resurrection campaign.
If the player begins the game on August 30, the PC starts with the lucky intrinsic and increases of +1 to Toughness and +3 to Mana. The message "You feel as if a whole new life is waiting for you!" is generated. If the PC also visits Lawenilothehl on this real-world day, an amulet of resurrection will be generated in Barnabas's shop.
Following an RFE during v. 1.2.0 development, as of ADOM v. 1.2.0 PCs that begin the game on October 31 start with candy treats — 1d6+2 blessed bits of plain candy and 1d2 blessed bit(s) of gnomish candy. The message "You feel treated." is generated.
Friday the 13th
Characters generated on any Friday the 13th will begin the game with the Cursed intrinsic. The message "You feel unlucky." is generated.
Characters generated on Mondays will start missing 2d2 hit points from their total. In practice, this has little effect on gameplay since these HP will recover quickly. The message "You feel slightly exhausted today." is generated.