[tz] Leap year bugs

Paul Eggert eggert at cs.ucla.edu
Wed Jan 22 19:37:27 UTC 2020

On 1/22/20 10:32 AM, Matt Johnson-Pint wrote:
> Why are Y2K and Y2038 bugs such a hot topic when they are/were one-time 
> events, but yet leap year bugs are rarely discussed even though they are 
> recurring and can have critical impact?

Possibly it's the same reason our nightly news covers shootings and car 
crashes even though the leading cause of death is heart disease.

> Are any of you working on leap year related issues?  Have you checked your date math for leap year bugs?

I'm not working on it. In the past I have checked date math for leap 
year bugs, and errors are common.

Leap year bugs can be pretty obscure, though. The most recent leap-year 
bug I recall fixing in tzcode was to support leap years where the year 
number can't be expressed in 32 bits. The notion of "leap year" makes no 
astronomical sense that far in the past or future anyway, so the bug 
wasn't that big a deal.

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