How to Count Anniversaries: Founding Anniversaries and a Chart of Wedding Anniversary Names

Anniversaries count full years; "the Nth year" counts inclusively

An anniversary counts how many full years have passed since the starting date. The starting date itself is the 0th anniversary, and the same date a year later is the 1st anniversary. "The Nth year", on the other hand, counts the year containing the starting date as year 1. Even when they refer to the same day, the numbers always differ by 1.

Saying internally "we've entered our 7th year" while announcing a "6th anniversary" externally isn't a contradiction. Confusion arises when an announcement uses both. Once you decide to use anniversaries, keep every expression of years in that document in anniversary terms.

Start of business, incorporation and founding: what's the difference?

A company's anniversary count changes depending on which date you use as the start. For companies that incorporated after starting as a sole proprietorship, the start of business and incorporation are often more than 10 years apart.

• Public "XXth anniversary since our founding" announcements usually count from the start of business, because the phrase expresses how long the history is.
• Where years on the register matter (bidding qualifications, credit checks and so on), the incorporation date is used.
• For internal anniversary events, decide first whether to use the start-of-business or incorporation date and write it in the regulations. It stops the debate coming up every time.
• Even after a move, merger or name change, the incorporation date doesn't change as long as the legal entity continues.

Old company histories and registers may give dates in the Japanese era. To convert something like "昭和39年4月" (April, Showa 39) to the Western calendar, enter the era and year in the Japanese Era Converter. For years that span an era change, entering the full date gives the correct era.

Chart of wedding anniversary names

Wedding anniversaries have names for each number of years. The basic pattern is that materials get harder and more valuable as the years go up, and they're used as a guide for choosing gifts.

The most widely used are the 25th (silver) and 50th (gold). In Japan, these two are sometimes the subject of awards from local governments and companies. Names vary by country and source, and some years have several names, such as tin or aluminium for the 10th. When writing an invitation, decide which source you're following so the naming stays consistent.

Celebrations of a person's age, such as kanreki and koki, are a separate system from wedding anniversaries. Since the custom of celebrating by kazoedoshi (traditional age) survives, see Japanese Longevity Celebrations if you want to check how they're counted.

February 29, and spanning Japanese era changes

• If the start is February 29, there's no matching date in common years. Some celebrate on February 28 and others on March 1. Writing "the last day of February" in internal regulations avoids deciding every time.
• Since the actual date only comes once every 4 years, some companies hold anniversary events in years divisible by 4.
• If the start is recorded in the Japanese era, changing eras doesn't change how anniversaries are counted. Converting to the Western calendar and subtracting gives the same result.
• "Founded in Reiwa 1" means founded on or after May 1, 2019. January to April of the same 2019 was Heisei 31, so if you don't check the month you can be a year out.
• If the company name has changed since incorporation, mentioning the former name in announcements lets business partners trace the history.

How leap years themselves work is covered in How Leap Years Are Calculated. There's an exception every 100 years, so it's worth knowing when dealing with long-cycle anniversaries.

When to start preparing for an anniversary

1. 1

   Fix the starting date

   Decide between the start-of-business and incorporation date and share it internally with the supporting documents (register, company history, articles of incorporation). Start preparing while this is vague, and a debate over the number of years will break out just before the announcement.

2. 2

   Count the remaining days

   Enter the starting date in the anniversary countdown of the Age & Anniversary Counter to list the days remaining until that date, plus total days and anniversary milestones. It gives you a starting point for planning backwards.

3. 3

   Work back from things that need ordering

   Commemorative gifts, printed materials and promotional items have long lead times. Fix the specifications 6 months before the anniversary. If you're redesigning the logo, you need to start even earlier.

4. 4

   List every existing mention

   Website, business cards, envelopes, email signatures. List everywhere it says "founded XX years ago" first, decide on a switchover date, and update them all at once.

5. 5

   Decide what happens the following year too

   Decide at the outset whether the anniversary logo will be used for a year or just on the day. If you don't, anniversary logos from years ago linger on.

If you're refreshing your logo for the anniversary, the scope of replacements is wider than you'd think. Criteria for deciding and a breakdown of the work are in Renewing a Logo.

FAQ

Which is correct, "6th anniversary" or "7th year"?

Both are correct; they're just counted differently. An anniversary counts full years since the start, so a company started on April 1, 2020 reaches its 6th anniversary on April 1, 2026. "The Nth year" counts the year containing the start as year 1, so the same day is year 7. They always differ by 1. Anniversaries are common in public announcements and "Nth year" internally, so don't mix both in one document.

Should an anniversary count from the start of business or incorporation?

Public "XXth anniversary since our founding" announcements usually count from the start of business, the day the business began. The incorporation date is when it was registered as a legal entity, which you can check on the commercial register. For companies that incorporated after a sole proprietorship, the two can be more than 10 years apart. Since incorporation dates are used where years on the register matter (bidding qualifications, credit checks), deciding in internal regulations which date anniversaries count from avoids debating it every time.

How many years are silver and golden wedding anniversaries?

Silver is 25 years and gold 50 years of marriage. Both are counted in full years, so they fall on the day exactly 25 or 50 years after the wedding. Others include paper for 1 year, wood for 5, tin (also called aluminium) for 10, crystal for 15, china for 20, pearl for 30, ruby for 40 and diamond for 60. Names vary by source, so keep the naming consistent when writing invitations.

If the start date is February 29, when do you celebrate?

There's no rule; some celebrate on February 28 and others on March 1, because February 29 doesn't exist in common years. Writing "the last day of February" in internal regulations or announcements removes the need to decide each year. Some companies make use of the actual date coming only once every 4 years by holding the anniversary event itself in a leap year. In Japanese age calculation, by the way, someone born on February 29 is treated as turning a year older at the end of February 28.