Jehovah's Witnesses do not celebrate holidays such as Christmas, Easter, and birthdays because they believe these celebrations have pagan origins and are not supported by the Bible. They focus on commemorating events such as the Memorial of Christ's death instead.
This also applies to all Muslims and some Buddhists.
Jehovah's Witnesses
In the book they do not celebrate Christmas which is the only mentioned holiday, (besides birthdays).
Depends on your religion.
yes. every culture and religion celebrates birthdays, because it isn't a religious holiday
There are no specials days or holidays for Sikhs, though Sikhs do celebrate the Birthdays of Sikhs Gurus and other important events.
Yes. Mormons, or as they are officially known as members of the Church of Jesus Christ of Latter-day Saints, celebrate all major Christian, community, and national holidays, as well as birthdays, anniversaries, etc.
There is no requirement to celebrate them. But many countries have made the birthdays of their heros national holidays. In the US, Presidents' Day and Martin Luther King, Jr.s birthdays are celebrated.
Muslims do not celebrate Valentines day, Easter, Christmas and many other european traditional holidays which have no concept in Islam. Many even don't follow birthdays like mostly christians do.
Yes. Although they do not celebrate Christmas for Santa Claus, presents, etc they still follow the traditions that most people follow. They will usually put a tree up if they have small children.
Religion isn't part of Harry Potter but considering he doesn't celebrate Jewish holidays then probably not.