UTC, Tai, and Unix Time (2001)
Leap seconds and the alignment of civil time with Earth’s rotation are under intense scrutiny, with many arguing they cause needless complexity in computer systems while offering little practical benefit to humans. Commenters contrast UTC (tied to solar time and leap seconds), TAI (a monotonic atomic timescale), and Unix/POSIX time, debating whether systems should standardize on TAI internally and relegate leap adjustments to higher-level conversions, especially as leap seconds are slated to be phased out by 2035. Broader ideas surface around abolishing daylight saving time and even time zones, highlighting the tension between precise, machine-friendly timekeeping and human expectations tied to the sun and local social rhythms.
Leap seconds: keep them or kill them?
- Many argue leap seconds are unnecessary complexity. Their cumulative effect is tiny over human timescales, and any eventual drift can be handled by rare time‑zone changes.
- Others defend them as a way to keep civil time aligned with Earth’s rotation and human biology, comparing future large corrections to the Julian→Gregorian transition.
- Some see abolishing leap seconds as “ignoring nature”; critics reply that modern life already diverges heavily from natural cycles and that precision users should rely on other timescales anyway.
- There’s disagreement on whether long‑term drift (hours over millennia) matters enough to justify ongoing complexity today.
UTC, TAI, POSIX, and Unix time
- TAI: monotonic atomic time with fixed-length seconds; ideal for logging, ordering events, and high‑precision systems.
- UTC: hybrid linked to both TAI and Earth rotation via leap seconds; good for human “clock on the wall” use.
- POSIX/Unix time: integers that mostly follow UTC but effectively assume 86,400 seconds per day, creating ambiguities on leap‑second days and breaking both “pure seconds since epoch” and “clean calendar” interpretations.
- Several commenters argue everything critical should use TAI internally, with UTC/local time as a presentation layer plus a leap‑second table.
Standards and the 2035 change
- Multiple comments note that international bodies have decided to stop inserting leap seconds into UTC by around 2035.
- Some see this as overdue simplification driven largely by IT; others worry about long‑term desynchronization and foresee future “big bang” corrections (e.g., leap minutes/hours) being worse.
Alternatives and design trade‑offs
- Proposed alternatives include:
- Leap minutes or rarer, larger adjustments (with debate about “tech debt” and future bugs).
- Handling leap seconds as first‑class entities, not hidden quirks.
- Letting time drift and adjusting time zones occasionally instead of UTC.
- More radical reforms: abolishing DST, abolishing time zones, or redesigning the calendar; these are mostly viewed as unrealistic or harmful despite some perceived simplicity.
Software handling and practical pain
- Real systems often “smear” leap seconds, pause or jump clocks, or ignore them, leading to inconsistent behavior.
- Time zones already require a database; several argue leap seconds should be treated similarly.
- Consensus that timekeeping is surprisingly tricky; incorrect assumptions about UTC behaving like TAI cause many bugs.