About This Site
About itsudakke.com - Japanese age calculator, data accuracy, and contact information
Introduction
“What year is it in Japanese era?” “When was my grandmother born in Showa?” “What year did I graduate high school?”
—This site aims to answer these everyday questions instantly.
Why I Created This Site
I’ve been running this site independently since 2025.
Throughout my life—university part-time jobs, job hunting after graduation, and subsequent career changes—I’ve written countless resumes. Each time, I found myself puzzling over “What year did I graduate high school? What’s that in Japanese era?” and had to look it up every time. Dealing with government offices, I often struggled with the Japanese era (Wareki) I rarely use in daily life.
Initially, I created this site to solve my own problems.
I also do volunteer work in social welfare, where I meet people from all walks of life. Not everyone follows the standard path of entering elementary school at 6 and progressing straight through. That’s why I added the ability to adjust for gap years, repeating grades, or leaves of absence.
Through the same volunteer work, I often talk with elderly people. I wanted to create a site where we could look back together at the society when they were young—at 10, at 20. The feature to trace someone’s life in 10-year intervals was born from this desire.
Features
- Age Reference Chart: Coverage from 1905 to 2026—122 years of data
- Japanese Era, Zodiac, Yakudoshi, Longevity Celebrations: Comprehensive Japanese calendar culture
- School Year Chart: Adjustable for gap years, repeating grades, leaves of absence
- Historical Events: Politics, society, sports background for each year
- Life Journey: Trace society at ages 10, 20, 30… in 10-year intervals
Data Accuracy
Calculation Logic
| Item | Method |
|---|---|
| Age | Calculated from Western calendar |
| Yakudoshi | Uses ‘counting age’ (kazoedoshi): current year − birth year + 1 |
| Adult Age | Lowered to 18 from April 1, 2022 (Civil Code revision). Coming-of-Age ceremonies remain at 20 in most municipalities |
| School Years | Based on April enrollment, March graduation |
Reference Sources
- Japanese Era, Zodiac: National Astronomical Observatory of Japan
- Yakudoshi, Longevity Celebrations: Based on common standards from Shinto shrines
- Historical Events: Summarized from major news sources and encyclopedias
About Early-Born (Hayaumare)
Calculations on this site are based on being “born on or after April 2.” For those born January 1 - April 1 (early-born), enrollment and graduation years are one year earlier. This is noted on each page.
Updates
- New year pages are automatically generated on January 1
- Previous year’s events are added after the new year
- Please contact us if you find any errors
Contact
For data corrections, feature requests, or other feedback, please use the contact form on the homepage.
Disclaimer & Privacy Policy
For terms of use, advertising, and cookie handling, please see our Disclaimer & Privacy Policy.