What do you do on Seijin-no-hi?

What food do you ear and what do you do?
Are there any special places people go?

The day is usually celebrated at the local city office on the second Monday of January. It is attended by those who have attained/ will attain the age of 20 bewteen Apr 2 of the previous year and Apr 1 of the current year.

Ladies usually wear Furisode (a type of Kimono). Men traditionally wear Hakama, but these days it is common to attend the ceremony in suit and tie.

The newly pronounced adults usually have a party in groups after the ceremony. What they eat is probably a matter of preference, but more often than not what they drink would have alcohol in it.

If he/she is a person over (not including) 20 years old, it's only a holiday for him/her.

If he/she is just 20 years old or will reach the age within the same year (beginning from April, ending in March), he/she can attend an official welcome ceremony for celebrating "newbie" adult people. Usually, when attending this ceremony, they (adult "newcomer" people) wear traditional clothes like kimono, but of course there are people wearing suit and tie.

After attending the ceremony, some of them drink alcohol, eat Shidashi Bento (Delibery Lunch) or Shidashi Sushi (Delivery Sushi) looking like this:
http://photozou.jp/photo/photo_only/313110/128536596?size=1024
http://ameblo.jp/balance-club-yokosan/image-11137864036-11739094175.ht...

Because this is their first official experience of drinking alcohol,
some of them are drunken, and a few of them cause a big trouble with other people.