However If We Take Into Consideration The Release Date Of Every Vocaloid Except Miku Who Will Always Be 16 Anyways - Tumblr Posts

Only one date is ever mentioned in-game, that being 2021. Considering that the Virtual Singer Fan Festa seems to be a stand-in for Magical Mirai 2021, we can assume that the Scramble Fan FESTA! event takes place in September 2021 (the real-life MM2021 was delayed to November due to covid-19, but the pandemic doesn't exist in-universe and MM Tokyo usually takes place at the beginning of September). There are Leo/need Daily Life social media posts that show them attending Magical Mirai, and do state the year of the event, but these can be considered promotional material for the event itself rather than canon material, especially since the characters address in-game that only one year has passed since the start of the story (despite the fact they have celebrated new year's day 4 times now. Timeloop things).

Based on this date, we can actually place exactly when every main character was born. The cutoff date for Japanese schools is April 1st, making Ena the oldest main character, being a 3rd year with a birthday of April 30th, followed by Tsukasa on May 17th, so on so forth all the way down to Kohane, a 2nd year with a birthday of March 2nd.

Considering when Scramble Fan FESTA is set, Ena, who was a 2nd year at the time, would be 17 years old. That would place her date of birth as April 30th, 2004. Additionally, while Kohane, a first year at the time, should be 15 during the event, the game considers her to be 16 due to using a set age for every grade bracket. Regardless, the event setting places her date of birth as March 2nd, 2006.

Based on this, we can conclude that:

Ena, Tsukasa, Rui, and Shizuku were born in 2004

Mafuyu, Kanade, Airi, Minori, Saki, Toya, Nene, An, Ichika, Mizuki, Emu, Haruka, Honami, and Akito were born in 2005

Shiho and Kohane were born in 2006

This also means that Ena, Tsukasa and Rui are all older than the MEIKO software (released November 5th 2004), and everyone except Kohane is older than the KAITO software (released February 17th 2006). Every main character is older than Miku, the Kagamines, and Luka based on this information.

Using the information around set ages*, we can also work out rough estimates for when the side characters were born. For example, Arata, who was 19 during the first 3 years of the game, is 3 years older than the members of VBS who were all considered to be 16. Since the members of VBS were born in the April 2005 - April 2006 school year range, Arata was likely born in the 2002-2003 school year range.

* based on how characters like Youta and Miu, who are said to be the same age as Leo/need, were both confirmed to be 16 years old before the 3rd anniversary age-up. Also Haruka's age is confirmed as 16 at a point in time when she shouldn't be 16. Timeloop things.

Based on this, the oldest side character, Kounosuke, who was 55 pre-3rd anniversary and 39 years older than Emu, was probably born between April 1966 and April 1st 1967. On the younger side of things, Hanano, who was 14 pre-3rd anni, was likely born between April of 2007 and 2008. I've put the rest of the estimated side character DOBs under the cut.

assumed age as of 3rd anniversary in brackets (literally just pre-age-up age + 1)

Kounosuke Otori - April 2nd 1966 ~ April 1st 1967 (56)

Jean Riley - 1967~1968 (55)

Harumichi Aoyagi - 1968~1969 (54)

Shin'ei Shinonome - 1973~1974 (49)

Mr Yoisaki - 1975~1976 (47)

Ken Shiraishi - 1978~1979 (44)

Taiga Kotaki - 1978~1979 (44)

Yuuka Kazamatsuri - 1990~1991 (32)

Keisuke Otori - 1991~1992 (31)

Shousuke Otori - 1994~1995 (28)

Tatsuya Okazaki - 1999~2000 (23)

Ayaka Saito - 2001~2002 (21)

Hinata Otori - 2001~2002 (21)

Iori - 2002~2003 (20)

Mio - 2002~2003 (20)

Arata Tono - 2002~2003 (20)

Souma Miyata - 2002~2003 (20)

Kotaro Mita - 2004~2005 (18)

Sakurako Seiryuin - 2004~2005 (18)

Nanami "Nanamin" Hayakawa - 2004~2005 (18)

Futaba Natsuno - 2004~2005 (18)

Asahi Genbu - 2004~2005 (18)

Ayumi Tabata - 2004~2005 (18)

Hibiki Miyake - 2004~2005 (18)

Shuuta Hayashi - 2004~2005 (18)

Ibuki Taniyama - 2004~2005 (18)

Yuina Uchiyama - 2005~2006 (17)

Shouta Hayashi - 2005~2006 (17)

Miu Takagi - 2005~2006 (17)

Youta Yoshizaki - 2005~2006 (17)

Riho Hasegawa - 2005~2006 (17)

Saku Kousaka - 2005~2006 (17)

Mai - 2006~2007 (16)

Hanano Yoshizaki - 2007~2008 (15)

Additional notes (mod is rambling atp):

We know that Kanade's mother died aged 30, and Rakunosuke died aged 98, but we do not know when they died. They are both still alive in flashbacks set roughly 10 years prior to the events of game.

We do not have confirmed ages for Shindou, Arisa, Nagi, Reki, Mafuyu's parents, and Yuuki (Mizuki's sister) yet.

Considering Arisa was in a group with Shizuku, they are probably somewhat close in age. Obviously idol groups can have age ranges of several years, but Arisa's design is also closer to that of the MC designs, so she's likely somewhere around her late teens.

Yuuki left for university when Mizuki was 15, making her at least 3 years older than Mizuki. Next to the Unchanging Warmth suggests that it's a bigger gap than that.

Rui says that Asahi is the same age as him and Sakurako in A Story Where You Are the Star. Unless a fanbook eventually confirms otherwise, he is 18.

Rui also suggests that Reki is the same age as him in A Story Where You Are The Star. However since it's more vague than Asahi, I left it out. For now at least. I might come back and edit this at a later date, because he does use the same general character design as the teenagers too.

Nagi's age is left blank in the fanbook due to it not being revealed that she was dead at the time of publication. She is younger than Taiga, but we don't know by how much, but nonetheless she was likely born in the early 1980s.

No NPCs are given exact birthdays