What is kanreki?
Kanreki is a word used to designate someone’s 60th birthday. What is the significance of sixty? In the 7th century, Japan began to use a Chinese calendar. The calendar was based upon the twelve Chinese zodiac signs (jūnishi) and the ten calendar signs (jikkan). Each year would be represented by a zodiac sign paired with a calendar sign. The least common multiple of the twelve Chinese zodiac signs and the ten calendar signs is sixty, so this is why one kanreki cycle is sixty years.
There are also other milestone birthdays:
koki 70 kiju 77
It is said that a person begins their second life once they have completed a sixty-year cycle. While the practice not as widespread as it once was, there is a custom where a person celebrating their 60th birthday dons a red hat called an akazukin and a red vest known as a chanchanko. Red baby clothes have been used as a good luck charm for infants, so since a person marking their 60th birthday has “been reborn,” this is why they wear red clothes.