Convert epoch/Unix timestamps to dates and dates to timestamps with millisecond precision and timezone handling.
Epoch Converter translates numeric Unix timestamps into calendar dates and converts calendar dates back into epoch values. It retains milliseconds and can present or interpret the date in a chosen timezone. The most common mistake is confusing seconds with milliseconds: a timestamp expressed in milliseconds is 1,000 times the corresponding seconds value. Timezone selection affects the displayed or entered calendar time, but an epoch timestamp itself identifies the same instant worldwide.
A concrete input and expected output from the current implementation.
Input
Timestamp: 0; timezone: UTC
Expected output
1970-01-01T00:00:00.000Z
Unix timestamp zero is the Unix epoch, midnight at the start of January 1, 1970 in UTC. The .000 portion records zero milliseconds, and Z denotes UTC.
The conversion measures elapsed time relative to 1970-01-01 00:00:00 UTC. A seconds value advances the instant by that many seconds; a millisecond value uses thousandths of a second. Converting in the other direction calculates the corresponding elapsed amount from the same origin, preserving the date's millisecond component.
An epoch value identifies an instant without carrying a timezone. A timezone supplies the local year, month, day, and clock time used to represent that instant. For date-to-epoch conversion, the entered wall-clock time must likewise be interpreted with an offset or timezone before it can identify one instant and produce one timestamp.
No. Traditional Unix time is commonly represented in seconds, while many software systems store milliseconds since the same epoch. The values therefore differ by a factor of 1,000. Check the source format instead of relying only on digit count, especially for older dates, negative values, or values containing a fractional part.
No when converting an existing epoch value to a date: the instant remains fixed and only its local representation changes. When converting a timezone-free calendar date to an epoch value, however, the chosen timezone matters because the same wall-clock reading can refer to different instants in different zones.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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