Birthday

A birthday is an occasion when a person or institution celebrates the anniversary of their birth. It is not to be confused with birthdate, which details the exact date a person was born. Known activities during birthdays include holding parties and feasts, as well as supplying the celebrant a birthday cake to share among both themselves and attendees, and also giving gifts to the celebrant.

Usage in the Dead or Alive series
Birthdays play an important role in Dead or Alive Xtreme Venus Vacation, where they are the subject of week-long gachas where, upon rolling 5,000 paid V-stones once, the player gets a cake to give to the celebrating girl, which supplies the player with an Extra Episode focusing on that particular girl's birthday of a given year. During the first year of the game (November 2017-October 2018 in the DMM version, and to a lesser extent May 2019-March 2020 in the Steam version), giving a girl a birthday cake only resulted in the girl being given the extra episodes, and rolling the birthday gacha did not supply any additional bonuses beyond the cake, while the gacha generally had past SSR and SRs for various girls (including paid star coin SSRs for add-on girls). In the second year, however, rolling in the gacha also supplied 10 candles in the girl's likeness, and also had the cake be utilized as furniture inside the Owner Room, with the gacha itself also allowing for a chance to roll for an exclusive Stella swimsuit (based on constellations, and in turn alluding to the Tropical Zodiacs that the girls' birthdays' fall under). Similarly, the extra episodes during the first year did not have any additional elements beyond gifting a cake, but in the second year, the episodes also have the owner supplying the birthday girl with the Stella swimwear as well as photographing them (with the player optionally taking the picture directly). Some of the girls can even get optional SR accessories for their Stella suits during the birthday periods by either paying 500 character coins in their likeness, or in the case of Tamaki and Ayane, paying 10 candles. The concept was further expanded in the third year, where the player can not only do all the elements introduced in prior years, but upon gifting the cake can also unlock an exclusive event where the player can win 1000 V-stones via an S-rank on each rank barring SS-Rank, which instead has the player unlocking a SSR+ "Promise Ring" as well as a pose of the girl showing off their ring (with the pose being automatically placed in their pose options on the camera menu upon being unlocked). The Promise Ring unlocks an extra episode where the girls are given their promise rings. In addition, accessories could also be unlocked if the player fully awakens the birthday swimwear (this time modeled after birthstones). Gemstones act as the currency during Year 3.

Although not explicitly birthdays due to having unknown birth dates, the characters Nyotengu and Kanna have a similar celebration known as Special Days, including being gifted birthday cakes and (in the case of year 2 and 3), swimwear and rings. Nyotengu in her first special day episode implies that "special day" was the term used by Tengu for what humans called birthdays.

The Steam version, while otherwise following the path of the DMM version, released the Stella swimwear early starting with Nyotengu, and also added presents that can be won during the Birthday/Special Day celebration event matches, with each gifted present to any girl rewarding the player with thank you cards, which can be used in a special event shop menu to purchase the girls' favorite food and drinks as well as character coins.

Aside from the celebration of girls birthdays, logging in during the player's own inputted birthday will have the girls give their own birthday salutations.

Trivia

 * Nyotengu and Kanna's special day dates, November 19 and September 15, fall around the dates of the release of Dead or Alive Xtreme Venus Vacation and Tokyo Game Show, respectively.