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SESK: Stuff Everyone Should Know · sesk.info/tech-y2k-two-digit-years

What caused the Y2K problem?

Years stored as two digits, so 00 could be read as 1900.

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  1. Clocks that could not show midnight
  2. Computers running out of memory in 2000
  3. Years stored as two digits to save memory ✔

Why: Early computers had very little memory, so programmers stored 1968 as 68 and assumed the 19. When 2000 arrived, 00 could look like 1900, breaking date math like ages, interest and expiration dates.

Huh, didn't know that: Credit cards expiring in 2000 or later were sometimes treated by old systems as expired almost a century earlier.

The dad joke
The Y2K bug was afraid of commitment. It could not handle more than two digits.
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References

Answer: Years stored as two digits to save memory. Early computers had very little memory, so programmers stored 1968 as 68 and assumed the 19. When 2000 arrived, 00 could look like 1900, breaking date math like ages, interest and expiration dates.

  1. US Senate Special Committee on the Year 2000 Technology Problem report (GPO, S. Prt. 106-10) govinfo.gov/content/pkg/GPO-CPRT-106sprt10/pdf/GPO-CPRT-106sprt10-6-1.pdf
    To save memory in the early days of computing, programmers represented four-digit years with only two digits.
    Checked 2026-10-10.

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