Timestamp interrogation desk · one number, four possible units
A number is not an instant until its unit is known.
Unix time is timezone-free arithmetic. Civil dates are policy. This converter keeps the unit gate, sub-millisecond remainder, UTC instant, and named-zone display on separate evidence rails.
54,202 CE
unlikely API payload
2024-03-09
common browser clock
1970-01-20
database precision
1970-01-01
system trace precision
Magnitude can suggest a unit; only the producing contract can prove it.
Try a timestamp with a known answer
Use the same instant to compare seconds, milliseconds, and an explicit UTC offset. The nanosecond example shows where the display stops preserving digits.
Loading an example replaces the current input and options. Relative time changes with your clock; the UTC values below stay fixed.
Convert epoch seconds to UTC
To Date · seconds · UTC. Select the unit explicitly instead of relying on digit count.
Input
1710000000
The UTC instant is March 9, 2024 at 16:00. Its millisecond value has three more zeroes.
2024-03-09T16:00:00.000Z 1710000000000
Read a JavaScript millisecond timestamp
To Date · milliseconds · Asia/Shanghai. Only the civil display uses the selected timezone.
Input
1710000000000
UTC stays at 16:00 on March 9; the Shanghai display moves to 00:00 on March 10.
2024-03-09T16:00:00.000Z 1710000000
Preserve a trace timestamp below one millisecond
To Date · nanoseconds · UTC. Keep the input as text so JavaScript number rounding cannot alter it first.
Input
1710000000123456789
The epoch ledger keeps all nine fractional digits. ISO shows .123 milliseconds plus an explicit 456789 ns remainder.
1710000000.123456789 2024-03-09T16:00:00.123Z · plus 456789 ns below the displayed millisecond
Convert an ISO date with an explicit offset
To Epoch · UTC display. The +08:00 in the input identifies the instant.
Input
2024-03-10T00:00:00+08:00
Midnight at +08:00 is 16:00 UTC on the previous day and equals the seconds example.
2024-03-09T16:00:00.000Z 1710000000
Signed epoch-zero axis
before 1970
1970-01-01T00:00:00Z
+ 16m 40s
current observation
same signed scale
One-instant ledger
Wall-clock customs
An offset turns a wall clock into an instant.
2026-11-01T01:30AMBIGUOUSDST overlap in some zones2026-03-08T02:30MAY NOT EXISTDST gap in some zones2026-08-03T10:00ZEXPLICITUTC instant2026-08-03T10:00+08:00EXPLICITsame instant as 02:00ZPrecision bridge
integer evidence
digits preserved
millisecond display
civil-time projection
Incident board
milliseconds divided twice
seconds treated as milliseconds or the inverse
unit contract missing at API boundary
timezone-less ISO parsed by environment
nanoseconds rounded into Date
Leap-second boundary
POSIX seconds are not an astronomical clock.
Unix/POSIX time does not number leap seconds as distinct instants. Use a timescale-aware system when UTC leap events or astronomical time are part of the requirement.
Follow a timestamp to its source
JWT NumericDate values use epoch seconds. Decode the token first, then convert the individual claim.
Format the surrounding response and check which field and unit the producer documents.
Use the local offline toolbox when investigating logs repeatedly.