What does shinnenkai mean?
Shinnenkai (新年会) is a Japanese custom at the beginning of the year. It literally means "New Year (shinnen) party (kai)", so it is basically a drinking party which is held in the early January.
It is the most common to have a big "shinnenkai" with co-workers, but people can have it with anyone like friends, club and team members, and so on. Basically, it seems that the most (drinking) parties are called "shinnenkai" as long as it is held in January.
When and Where?
Since it is common to have shinnenkai with co-workers, the party is usually set up on Friday or Saturday night in January, so they can get drunk without any worries about the next day. Generally, people tend to gather and spend time with their family at the very beginning of the year, so shinnenkai is often held after the first week of January.
They are likely to go to izakaya (Japanese style casual bar), for the izakaya offers a big capacity for large groups of people and also has reasonably priced course meals that include "nomihodai" (all-you-can-drink).
Shinnenkai is a very common event at the beginning of the year that people are looking forward to having. How about joining the party and helping yourself drinking to start off a good year?
Do you know Bonenkai?
You should check Bonenkai out too! It is a similar kind of Japan's drinking parties at the end of the year.