UTC
—
Coordinated Universal Time
ISO 8601
—
Machine-readable standard
Swatch .beat
—
@000–999 · no timezones · BMT UTC+1
Unix
—
Seconds since 1970-01-01Z
Unix ms
—
Date.now() · JavaScript standard
Unix hex
—
32-bit overflow → Y2K38 · 2038-01-19
GPS Time
—
Week + TOW · +18s from UTC · no leap sec
TAI
—
Atomic · UTC +37s · continuous
TT
—
Terrestrial Time · TAI +32.184s · ephemeris
Julian Date
—
Days since 4713 BC Jan 1, noon
MJD
—
JD − 2400000.5 · epoch 1858-11-17
Seconds today
—
of 86,400
Loran-C era
—
Days since 1958-01-01