So, most games are "supposed" to have a BCD representation of the years passed since the start of the Japanese Showa era, here calculated by adding 1925 to the value. Thus, most games have a date starting at $61 in BCD = 1986, and counting up.

(There are two homebrew controller test disks out there, and they have date codes of $94 and $95, showing they were made in the years 2019 and 2020.)

But then I wondered if anything changed when the Heisei era began in 1989, and, yep, a number of games began numbering their date fields starting at $01 in 1989. Some stragglers remain, however, counting up from the Showa era even into the 1990s.

**YuuYuuki**and

**Famicom Tantei Club II**have date values of $01, meaning 1988+1=1989.

**Knight Move**has a value of $02, meaning 1990.

**Clu Clu Land**, as an oddball example, has a rewritten value of $68, meaning 1993 adding from 1925.

**Zelda no Densetsu v1.0**and its prototype have values of $85 and $86, meaning they store the Gregorian date in BCD. I wonder if there are any other examples like this out there...

And then there are the odd few games whose copyright or written dates I can't figure out. So, some examples:

**Wrecking Crew**has a Rewritten date value of $72. Counting from Showa, that makes the year 1997. Not impossible, but... I have my doubts.

**SD Gundam Gachapon World**(Disk Writer) has a date of $73.

**Puzzle Boys**and

**Pinball**have a date of $74.

**Goonies**and

**Donkey Kong**have Copyright dates of $77!

Perhaps this has some special meaning when games are created on the Disk Writer.

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So the simple rules that I had to add to FDSList are as follows:

For date codes $01-$60, add 1988 (Heisei) to value.

For date codes $61-$99, add 1925 (Showa) to value.

For codes $85 and $86, single them out: just add 1900. (Apologies to the years 2010 and 2011.)

For codes $9A-$FF, they're invalid.

Is there any logic that I missed?