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canopic jug submitted this article:

Steven Bellovin, Professor of Computer Science at Columbia University writes briefly with a concrete example of how the Y2038 threat works.

[...] just as with Y2K, the problems don't start when the magic date hits; rather, they start when a computer first encounters dates after the rollover point, and that can be a lot earlier. In fact, I just had such an experience.

A colleague sent me a file from his Windows machine; looking at the contents, I saw this.

$ unzip -l zipfile.zip
Archive: zipfile.zip
Length Date Time Name
——— ——— ———
2411339 01-01-2103 00:00 Anatomy...
——— ———

Look at that date: it's in the next century! (No, I don't know how that happened.) But when I looked at it after extracting on my [MacOS] computer, the date was well in the past:

$ ls -l Anatomy...
-rw-r-r-@ 1 smb staff 2411339 Nov 24 1966 Anatomy...

Huh?

After a quick bit of coding, I found that the on-disk modification time of the extracted file was 4,197,067,200 seconds since the Epoch. That's larger than the limit! But it's worse than that. I translated the number to hexadecimal (base 16), which computer programmers use as an easy way to display the binary values that computers use internally. It came to FA2A29C0. (Since base 16 needs six more digits than our customary base 10, we use the letters A–F to represent them.) The first "F", in binary, is 1111. And the first of those bits is the so-called sign bit, the bit that tells whether or not the number is negative. The value of FA2A29C0, if treated as a signed, 32-bit number, is -97,900,096, or about 3.1 years before the Epoch. Yup, that corresponds exactly to the November 24, 1966 date my system displayed. (Why should +4,197,067,200 come out to -97,900,096? As I indicated, that's moderately technical, but if you want to learn the gory details, the magic search phrase is "2's complement".)

While attention is paid to desktops and servers, they are easy to replace and have very short lifetimes. In contrast embedded systems should be receiving special action already since they are seldomly or never updated and have lifespans measured in decades.

Previously:
Reducing Year 2038 Problems in curl (2018)
The Time Is... 1500000000 (2017)

Original Submission