Greetings and salutations, and thanks for asking!

Japan has 16 National Holidays (please see below).
The dates of some holidays are changed to Monday to make consecutive holidays.

-New Year’s Day (January 1st)

-Coming-of-age Day (the second Monday of January) This holiday used to be on January 15th. It’s a day to congratulate children becoming adults. Japan has lowered the age of adulthood from 20 to 18 in 2022, but people under 20 are still banned from drinking alcohol and smoking.

-National Foundation Day (February 11th) Enthronement of the first emperor of Japan is recorded to have been in 660 B.C.E.

-Emperor’s Birthday (February 23rd) Emperor Naruhito’s birthday.

-Vernal Equinox Day (around March 20th)

-Showa Day (April 29th) Showa is the era when emperor Hirohito was on the throne (1926-1989). Showa day was Emperor Hirohito’s Birthday.

-Constitution Day (May 3rd) On May 3rd, 1947, the current Constitution of Japan came into effect.

-Greenery Day (May 4th) Originally, this holiday was celebrated on April 29th. This is a day to commune with nature and be grateful for its blessings.

-Children’s Day (May 5th) This day is traditionally the Boy’s Festival. (March 3rd is the girls’ festival day called the Festival of Dolls, but it isn’t a holiday.) We wish for children's happiness and growth, and value children's character.

-Marine Day (the third Monday of July) This is the day for expressing gratitude for the bounty of the sea, honoring its importance and praying for the prosperity of Japan as a maritime nation.

-Mountain Day (August 11th) Mountain Day is another day appreciating the blessings of nature.

-Respect-for-the Aged Day (the third Monday of September) The day to show respect for the elderly for the contributions they have made to the society and to celebrate their longevity.

-Autumnal Equinox Day (around September 23rd)

-Sports Day (the second Monday of October) This holiday used to be on October 10th. This day was the opening day of the Tokyo Olympics held in 1964. It is said that October 10th tends to be sunny in Tokyo, therefore, the day was chosen for the opening ceremony.

-Culture Day (November 3rd) The day is dedicated to the love of freedom, peace and the promotion of culture. Also, this was the birthday of the Meiji emperor.

-Labor Thanksgiving Day (November 23rd) The holiday is for celebrating labor and production and giving one another thanks. In the past, a traditional festival was held on this day to offer new rice to the gods.

Hope this helps and we wish you a nice day!