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Japanese Date Coding Systems

(This page revised July 5, 2020)

Reference Info Index | Glossopedia  ]

When Was It Made?

In many cases, finding out when a given pen was made is difficult if not impossible. For some Japanese pens, however, it can be easy. Pilot, Platinum, and Sailor have all applied date codes to their pens for many years, and at least one other manufacturer, Hatanaka Kōseido, appears to have done so as well. Note that some of the systems described here are applied to nibs, not to pen bodies; thus, if the nib has been replaced and there is no code on the body, then the nib — but not the pen itself — can be dated. If the nib has not been changed, the pen was most likely made in the same month as the nib or in the following month.

It is important, also, to remember that not all nibs are date coded. Steel nibs are typically not dated, but there are some that do have date codes. You are most likely to find undated gold or palladium nibs in pens with date codes on the pen bodies, but this too is not a universal rule.

In pen body images accompanying the descriptions of the various date codes, the codes have been filled with white wax to make them clearly visible. In each nib image, a red circle marks the location of the date code.


Pilot has used two dating systems. The first, introduced early in the company’s history, appears on nibs. The second, which was used for only a short period, appears on pen bodies, as described below.

For inset nibs like those on the Sterling and Elite 95S models, which are not easily removable, the date code is near the base of the nib, where it can be easily seen:


For other nibs, it can be in one of two locations: on the part of the nib that is concealed within the section or, occasionally, on the underside of the nib. You will have to remove these latter types of nibs to read their date codes.

On most Pilot pens that have a date code on the pen body, the code appears on the section or on the barrel, near the center joint. On Capless models with metal bodies and plastic pushbuttons, the date code is on the pushbutton. If it is in none of these locations, the only date code will be on the nib.

Location is a single letter indicating where the pen was made:
  • T: Tokyo factory (in Shimura, Itabashi ward)
  • H: Hiratsuka factory (in Kanagawa prefecture)
  • A: Hiratsuka, production line A
  • B: Hiratsuka, production line B
  • F: Thailand, Burma, India, or Brazil

Month is a one- or two-digit number, 1 = January to, 12 = December.

Year is a two-digit number, the last two digits of the calendar year in the Common Era.

The date code of H970 shown above indicates that the nib was made in Hiratsuka, in September 1970. The letter denoting the manufacturing location is sometimes omitted, especially on older pens. In 2010, Pilot eliminated the letter completely. For example, a date code of 1114 indicates that the pen was made in November 2014.

In theory, the potential for ambiguity exists in that a date code with a year of 15 could indicate a nib made in 1915 (the year in which Ryōsuke Namiki began producing gold nibs) or 2015, and similarly for years greater than 15; but on a practical level, it is a simple matter to identify the correct year by observing other features of the nib or of the pen as a whole.


Year is a single letter, A = 1960 to Z = 1985.

Month is a single letter, A = January to L = December if made in Hiratsuka; or M = January to X = December if made in Tokyo.

Day is a two-digit number indicating the day of the month.

The date code of KJ05 shown above indicates that the pen was made in Hiratsuka, on October 5, 1970. The year 1985, represented by the letter Z, would have been the last year for this system, but it appears that Pilot ceased using the system a few years earlier, in the early 1980s. Short lived as this system was, it provides the ultimate way to date a pen bearing it.


Date codes on Platinum pens appear only on the undersides of nibs, requiring you to remove the nib to read the code. Date coding began in 1953, when Platinum received certification from the Japan Industrial Standard Committee, and it was discontinued in September 2015. The system itself is very simple.


Month is a one- or two-digit number, 1 = January to 12 = December.

Year is a two-digit number, the last two digits of the year.

Things become a little less simple, however, because the system, as initially devised, used the traditional Japanese calendar, which is based on the year within the current emperor's reign. Thus, a year of 10 could mean 1921 (Taishō era, Emperor Yoshihito, year 10), 1935 (Shōwa era, Emperor Hirohito, year 10) or 1999 (Heisei era, Emperor Akihito, year 10). Platinum switched to the modern Western calendar, which uses the Common Era, either at the beginning of the Heisei era (when Akihito ascended the throne) or at the change of the millennium. Because it is not known which of these two dates applies, pens made from 1990 until 2000 could have years in the range from 65 to 75 or from 90 to 00. The date code of 547 shown above indicates that the nib was made in May of Shōwa 47 (CE 1972). Japanese–Western Calendar Conversion contains tables for converting between the two calendars.


Sailor has employed three datation systems. The first, a three-digit system, was used on nibs and, very briefly, on pen bodies. The second system, applied to nibs only, uses two digits and one letter. The third system, a two-letter system, was used briefly for pen bodies only.


Year is a single-digit number, the last digit of the calendar year in the Common Era.

Month is a two two-digit number, 01 = January to, 12 = December.

This system was introduced when Sailor began dating its products. Because only a single digit is used for the year, there are some ambiguities; for example, a date code of 306 could indicate a nib made in June of 1953, 1963, 1973, 1983, and so on. Accurate dating of a given pen therefore relies on your knowledge of the approximate period during which pen models that have used this nib were active. The nib above came from a Sailor pocket pen. The date code of 312 shown above indicates that the nib was made in December of 1973 or 1983, probably the former. In 2017, Sailor replaced this system with the second system, described below.

This system was also used briefly on pen bodies: from about 1971, when the third system (described below) was discontinued, until sometime in the mid-1970s. The latest pen I have seen with this system on the pen body is an Olympia pocket pen with a date code of 607, indicating July 1976. After retiring this system, Sailor appears to have ceased date-coding pen bodies.

Year is a two-digit number, the last two digits of the calendar year in the Common Era.

Month is a single letter, A = January to L = December.

For example, a date code of 18J indicates a nib made in October 2018. This system replaced the first system (described above) in 2017.

Sailor used two systems on pen bodies. Before 1960, pen bodies were not date coded. Beginning in 1960, there was a two-letter code. Either upper- or lowercase letters were used, with the case having no significance; thus, A and a meant the same thing. There might or might not be a dot between the letters; this dot also has no significance.


Year is a single letter, A/a = 1960 to K/k = 1970 (and possibly L/l = 1971).

Month is a single letter, A/a = January to L/l = December.

The date code of IE as shown above (or I.E or ie or i.e) indicates that the pen was made in May 1968. This system was phased out at the end of 1970 or during 1971 in favor of the same three-digit numerical system used on nibs, which was in turn discontinued on pen bodies after 1974.

Sailor pens bearing date codes on both the nib and the pen body are uncommon; if the body is date coded, there is most likely no date code on the nib, and vice versa.

Hatanaka Kōseido

The nib described here is identified by its JIS number imprint as having been made by Hatanaka Kōseido. It is imprinted RIEYON and was found in a Rieyōn pen. Not all authorities agree that the maker of Rieyōn pens survived into the 1980s. Treat the information in this section as an educated guess, not as established fact.

Outside the Big Three, Hatanaka Kōseido (Hatanaka Small Company) is the only manufacturer I have identified that appears to have date coded its products. The code is on the underside of the nib, at the base, and the system is quite simple:

Hatanaka nib

Week is a one- or two-digit number representing the week of the year in which the nib was made.

Year is a two-digit number, the last two digits of the year. Like Platinum, Hatanaka used the traditional Japanese calendar, which is based on the year within the current emperor's reign.

The date code of 41/56 shown above indicates that the nib was made in the 41st week (beginning Sunday, October 4) of 1981.

  1. Much of the information on datation systems is taken from a series of entries in Bruno Taut’s blog, Crónicas Estilográficas. I have reorganized and rewritten it for this article. Mr. Taut states in his blog that some of his information came originally from Japanese pen expert Masamichi Sunami, co-author with Andreas Lambrou of Fountain Pens of Japan.  Return

  2. In response to a query on this subject, the Platinum Pen Company’s representative stated that the company does not have records that would document any changeover in year notation and that the company believes that the system has remained unchanged throughout the period of its use.  Return

  3. In response to a query on this subject, the Sailor Pen Company’s representative stated that the company no longer has the records needed to substantiate this datation system. As used in this article, the system is based on one described by Bruno Taut in a 2015 blog post. I have found Mr. Taut’s reckoning of years to be impossible, however, and I have therefore used my own reckoning.  Return

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.

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