Unix Timestamp and Epoch in PHP

Unix time counts elapsed time from the Unix epoch at 1970-01-01T00:00:00Z. Different ecosystems use different units, so always label whether a value is in seconds, milliseconds, microseconds, or nanoseconds.

Quick Start#

The following example uses the standard PHP API or a widely used package for this task.

Quick start#

1<?php2$seconds = time();3$milliseconds = (int) floor(microtime(true) * );45echo $seconds . PHP_EOL;6echo $milliseconds . PHP_EOL;

Common Operations#

This second pattern covers a common production operation or a safer way to handle real input.

Convert with DateTimeImmutable#

1<?php2$dt = (new DateTimeImmutable('@' . $seconds))3    ->setTimezone(new DateTimeZone('UTC'));45echo $dt->format(DateTimeInterface::ATOM) . PHP_EOL;

Important Notes#

The @timestamp DateTime syntax starts in UTC; set an explicit display timezone afterward when needed.

Best Practices#

1. Treat external input as untrusted and handle parse/validation errors explicitly.
2. Keep encoding, units, formats, and library-specific mapping rules explicit at system boundaries.
3. Add test vectors that cover empty input, Unicode text, malformed input, and representative production data.

References#

• POSIX Seconds Since the Epoch
• PHP Manual