Blog

Short pieces about the same problems the calculators solve. Newest first, 12 posts per page.

• Time · 2026-08-14

  12-hour clocks, 24-hour clocks, and midnight

  12:00 a.m. is midnight, 12:00 p.m. is noon. Mixed formats are a common source of countdown errors.

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• Time zones · 2026-07-21

  DST gaps, folds, and time zone conversion

  Spring-forward removes an hour; fall-back repeats one. Converters should use IANA zones, not a handwritten UTC offset.

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• Dates · 2026-06-09

  Leap-day birthdays and civil age

  People born on 29 February still age one year per year. This site observes the birthday on 28 February in common years.

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• Dates · 2026-05-18

  What adding a month to 31 January should mean

  Month arithmetic is not the same as adding 30 days. This site clamps overflow to the last valid day.

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• Dates · 2026-04-02

  Inclusive vs exclusive day counts

  1 January to 3 January can be two days or three, depending on whether both endpoints are counted.

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• Timers · 2026-03-12

  Why countdown timers skip seconds in background tabs

  Browsers throttle timers in hidden tabs. Timestamp subtraction keeps remaining time honest when you return.

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