Omisoka December 31

Ōmisoka (大晦日^?), New Year's Eve, is the second-most important day in Japanese tradition because it is the final day of the old year and the eve of New Year's Day, which is the most important day of the year.
People tend to be very busy on Ōmisoka because they have much to do to prepare for the new year, and New Year's Day in particular. Many even do a thorough house cleaning, called ōsōji (大掃除). The exercise is much like the annual spring cleaning that people in most colder climates do and even involves changing the paper on shōji doors and setting tatami mats out to air in the sun. Similarly, on the final day of school before winter break, elementary school children do their own ōsōji to get their schools ready for the new year, and most businesses spend the year's final work day cleaning. The purpose of all this is to get ready to welcome in the new year with everything—including people's minds and bodies—in a fresh, clean state, making everything ready for the new beginning that New Year's Day is held to signify.

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Fiesta of Our Lady of Guadalupe - December 12

The Feast of Our Lady of Guadalupe is celebrated on December 12th.
In 1999, Pope John Paul II, in his homily from the Solemn Mass at the Basilica of Our Lady of Guadalupe, during his third visit to the sanctuary, declared the date of December the 12th as a Liturgical Holy Day for the whole continent.
During the same visit Pope John Paul II entrusted the cause of life to her loving protection, and placed under her motherly care the innocent lives of children, especially those who are in danger of not being born.

Hanukkah December 1-9

Hanukkah (Hebrew: חֲנֻכָּה‎, Tiberian: Ḥănukkāh, usually spelled חנוכה pronounced [χanuˈka] in Modern Hebrew, also romanized as Chanukah, Chanukkah, or Chanuka), also known as the Festival of Lights, is an eight-day Jewish holiday commemorating the rededication of the Holy Temple (the Second Temple) in Jerusalem at the time of the Maccabean Revolt of the 2nd century BCE. Hanukkah is observed for eight nights and days, starting on the 25th day of Kislev according to the Hebrew calendar, which may occur at any time from late November to late December in the Gregorian calendar.

December- multicultural celebrations

Saint Nicholas Day (Christian) -- December 6

Fiesta of Our Lady of Guadalupe (Mexican) -- December 12

St. Lucia Day (Swedish) -- December 13

Hanukkah (Jewish) -- Begins at sundown on December 1 (ends December 9)

Christmas Day(Christian) -- December 25

Boxing Day (Australian, Canadian, English, Irish) -- December 26

Kwanzaa (African American) -- December 26 to January 1

Omisoka (Japanese) -- December 31