PHP Unix Timestamp: time(), microtime & DateTime Zones

Get the current Unix timestamp

time() returns whole seconds. For milliseconds, use microtime(true), which returns a float in seconds with microsecond precision — multiply by 1000 and truncate.

PHP

<?php
$sec = time();                          // 1767225600 (whole seconds)
$ms  = (int) round(microtime(true) * 1000);   // milliseconds
$us  = (int) round(microtime(true) * 1000000); // microseconds

// microtime(false) returns "0.123456 1767225600" — parse it if you need both parts
list($usec, $sec2) = explode(' ', microtime());

Convert a timestamp to a date

Two idioms: the procedural date() and the object-oriented DateTimeImmutable::setTimestamp(). Both format in the default timezone — configured with date_default_timezone_set() or php.ini. Never rely on that default being UTC.

PHP

<?php
$ts = 1767225600;

echo date('Y-m-d H:i:s', $ts);          // uses the DEFAULT timezone

$dt = (new DateTimeImmutable())->setTimestamp($ts);
echo $dt->format('Y-m-d H:i:s P');      // e.g. 2026-01-01 00:00:00 +00:00

$ist = $dt->setTimezone(new DateTimeZone('Asia/Kolkata'));
echo $ist->format('Y-m-d H:i:s P');     // 2026-01-01 05:30:00 +05:30

Convert a date back to a timestamp

Parsing is where PHP's defaults bite hardest: strtotime() and new DateTime($string) interpret zone-less strings in the default timezone. For UTC input, use a Z suffix or build the DateTime from parts with an explicit zone.

PHP

<?php
$ts = strtotime('2026-01-01 00:00:00');           // DEFAULT zone — machine-dependent
$ts = strtotime('2026-01-01 00:00:00 UTC');       // explicit, deterministic

$dt = new DateTimeImmutable('2026-01-01 00:00:00', new DateTimeZone('UTC'));
$dt->getTimestamp();                              // 1767225600

// DateTimeImmutable::createFromFormat locks the format AND the zone
$dt2 = DateTimeImmutable::createFromFormat('!Y-m-d H:i:s', '2026-01-01 00:00:00', new DateTimeZone('UTC'));

Timezone-aware vs naive (and mutable vs immutable)

PHP's DateTime is always zone-aware — it always carries a DateTimeZone. The naivety problem is inverted: if you don't set a zone, PHP imposes the global default on you. The other trap is mutation: DateTime methods (setTimestamp, setTimezone) mutate the object and return $this, which makes copy bugs easy. DateTimeImmutable returns new objects and is the safe default.

PHP

<?php
// Mutable: both variables share one object
$a = new DateTime('2026-01-01', new DateTimeZone('UTC'));
$b = $a->setTimezone(new DateTimeZone('Asia/Kolkata'));
echo $a->format('H:i');   // 05:30 — $a changed too!

// Immutable: $a keeps its value
$a = new DateTimeImmutable('2026-01-01', new DateTimeZone('UTC'));
$b = $a->setTimezone(new DateTimeZone('Asia/Kolkata'));
echo $a->format('H:i');   // 00:00 ✓

Native precision: seconds

time() is whole seconds. Millisecond and microsecond values come from microtime(true) or from DateTime only after PHP 7.1's microsecond support in the constructor/format strings. Everything downstream is integer epoch — exactly what the converter expects when you paste a 10-, 13-, or 16-digit value.

Common pitfalls

Default timezone — set date_default_timezone_set('UTC') early, or every date() call shifts with the server.
strtotime('2026-01-01') — local midnight, not UTC midnight.
Mutable DateTime — setTimezone() changes the original; use DateTimeImmutable.
Timestamp range — 32-bit PHP wraps in 2038; run 64-bit builds (PHP 8 is 64-bit-only).

Try it live

Verify any value against these snippets in the main epoch converter, or copy the current timestamp from the PHP snippet tab on the homepage.