In the UK there are special calendars called Advent calendars that are used to count down the days to Christmas (クリスマスまでの期間に日数を数えるためのカレンダー).
Advent = 待降節の期間 – キリストの降誕を待ち望む期間
Traditionally the Advent season begins on the 4th Sunday before Christmas day (クリスマスの四つ前の日曜日) and ends on Christmas Eve, but most modern advent calendars start on December 1st.
Advent calendars are special because they have small windows on them that you can open for each date and inside you can find pictures or sometimes stories or poems. The calendars usually have a Chistmas or winter theme.
Recently, however, there are many kinds of calendars you can buy, sometimes with sweets or chocolate behind each door or even a small toy.
In the picture above you can see the calendar my children received from their grandparents in the UK this year, which is in a very traditional style.