software, Uncategorized

Classic Mac Y2K20 bug


Back in the day, Mac users generally shrugged off the dreaded “Y2K” problem. Macs since the beginning could store dates in 4 digits and work with dates well after 2000. However, back then we knew there was a time in the distant future where we would start running into date-related problems… unfortunately that time is now. Classic Macs may have trouble setting dates 2020 and beyond, but the good news is there’s a solution – at least for now.

The Roaring 2020s

This all started when my Color Classic Mystic’s PRAM battery died. (Finding one of those is a story in itself.) In any case I replaced the battery and set the date; June 29th 2020. The first sign of trouble was the “day of the week” was showing up incorrectly in the menu bar. Then to my surprise, all of the files I created got date-stamped as “June 29th 1920”.

I then checked another system, my SE/30. Since I did not have the date displaying the day of week in the menu bar, I was none the wiser that my clock was actually set to 1920, and not 2020! Next, I checked my Mac Classic… which was correctly set to 2020. What gives!?

Picture 2

The issue begins to become clear when using the Date & Time control panel. In it, I was able to set the 4-digit year up to 2019 – and as soon as you increment it up to 2020, it drops back to the 1900s! The control panel in System 7 and 8 only supports years up to 2019!

Macs apparently knew we didn’t want to deal with 2020 in general…

So now what? My clocks were only correct because I must have set them previously to 2020, and they obviously support dates after 2020. The good news is I figured out two ways to solve the issue…


Option 1: Network Time

If your classic Macintosh has the ability to reach the internet, one easy option is to use the Network Time control panel…

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In it, we can specify a time server, like “”, and click “Set Time” to synchronize the system clock to the server’s time. Done.

Download Network Time


Option 2: Set Date CDEV

If you do not have the ability to use Network Time, there is fortunately a control panel out there capable of setting the year post-2020, it’s simply called “Set Date”…


You can find out more and download a copy of “Set Date” at Low End Mac.


So, we’re good, right?

Well, yes – for the next 20 years at least. The Mac was designed to support dates from 1904 to 2040 due to the algorithm used for the calendar. You can read more about the date limitations in this old MacWorld article about Y2K.

The good news is we’ll have working Mac clocks for the next 20 years, and we still have 20 years to figure out a hack to address the 2040 limitation.