Unix Time reaches 1.7 billion

Original Article ↗ Hacker News Discussion ↗

Unix time recently passed 1.7 billion seconds since its epoch on January 1, 1970, prompting programmers to mark the moment with scripts, livestreams, and lighthearted numerology. Beyond the novelty of a round number, contributors use the milestone to explore deeper topics like leap seconds, differences between UTC, TAI and other time standards, and the looming Year 2038 problem for 32‑bit timestamps. Many note how these recurring epoch milestones serve as a kind of long-term metronome for people who work closely with timestamps.

Milestone and reactions

  • Unix time reached 1,700,000,000 seconds since 1970-01-01, prompting playful “celebration” posts and callbacks to earlier milestones (1.2B, 1.4B, 1.5B, 1.6B, 1.666…B, 1.6G, 1.5G, 1400000000, 1234567890, 1,000,000,000).
  • Some commenters find it fun “numerology” and treat these as rare, long-term metronome moments, even tying them to birthdays or personal memories.
  • Others are dismissive, questioning why a base-10 round-ish number matters, especially when similar thresholds occur every ~3 years.

Watching the rollover

  • People used shell loops (date +%s, watch), Node.js, Deno REPL, and ad hoc JS snippets (with setInterval, async generators, drift-correcting timers) to watch the counter tick.
  • A few recorded or livestreamed the event; others joked about “clinking calculators” or filming for replay.

Leap seconds, UTC, and what Unix time really is

  • Detailed debate over whether Unix time is “seconds since epoch” or “days×86400+seconds”, with emphasis that POSIX defines it as an approximation ignoring leap seconds.
  • Clarification that:
    • Leap seconds mean some real days are 86401 seconds, but Unix time assumes 86400.
    • This causes Unix time to diverge from actual elapsed SI seconds and from TAI.
    • Unix time does not have distinct values for leap seconds; some timestamps map to 2-second real intervals.
  • Discussion of different time standards and use cases: UTC for human activity, TAI/Unix/GPS for monotonic time, UT1/apparent solar/sidereal/TCB for astronomy and navigation.
  • Noted that UTC’s leap-second policy is being reconsidered; future “leap minutes” are mentioned.

Future milestones and the 2038 problem

  • People point to upcoming milestones: 1.8B in 2027, 2.0B in 2033, 2,147,483,647 (signed 32-bit max) and 2,147,483,648.
  • 2038 problem is discussed as a “next Y2K”: modern systems mostly use 64-bit timestamps, but legacy 32-bit and embedded devices (including ROM-burned code) remain a concern.
  • Some recall Y2K both as a genuine engineering effort and as overhyped doomsday; note that fear sometimes helps get systems fixed.

Epochs, calendars, and representation details

  • Debate over using 1970 vs “year 1” as an epoch; others note many calendar eras exist and Gregorian year numbering is itself arbitrary.
  • Mention that Go’s time representation uses year 1 and that very early machines made a year-1 epoch impractical.
  • One commenter argues strongly for TAI over Unix time for correctness.
  • Protobuf guidance: avoid variable-length integers for timestamps; fixed-size (fixed32/fixed64) is often smaller and faster.