Important 70s birthday help!

My mother is doing a birthday for a lady that is like 72 or 73. This lady's children said that this was an important birthday in Japan. I cannot find anywhere about this birthday. Please help!! I need to know the customs, and why it is important.

70th birthday going by the old Japanese age counting method, so 71 or 72 by the "modern" counting method, is called "Koki" ("old and rare"), and it is one of the 10-year anniversaries celebrated, because in the old days reaching 70 was considered rare and memorable. Maybe that's what their children are talking about.

Nowadays people do live longer, so 70 is not that rare lol, and some 70-year-olds don't want to be treated "old," so you can just celebrate hers just like any other birthday together with their family :) You can ask the family if there is anything the mother wants :) The traditional color used to celebrate this 70th birthday is purple, so maybe you can give something that has the color purple in it - that's the only traditional bit I can think of :)

Whoops, sorry, couple of mistakes!

- 70 by the old counting method should be 69 by the modern-day birthday.
- "Koki" means "rare since the olden times."
- If she is closer to 75, then it might be the next one, 77 by the old counting method, which would be "Kiju," "happy age," because if you write the number "77" using the kanji numbers, it looks like the kanji for "happiness."