How do I format dates in PHP?

Short answer

Use DateTimeImmutable with an explicit timezone and format with ->format(). Store timestamps in UTC and convert for display.

php

$now = new DateTimeImmutable('now', new DateTimeZone('UTC'));

echo $now->format('Y-m-d H:i:s');   // 2026-03-15 14:30:00
echo $now->format('l, j F Y');      // Sunday, 15 March 2026
echo $now->format('c');             // ISO 8601

#Why Immutable

DateTime methods modify the object in place and also return it, so this bug is easy to write:

php

$start = new DateTime('2026-01-01');
$end = $start->modify('+1 month');   // $start changed too!

DateTimeImmutable returns a new object and leaves the original alone. Use it by default.

#Format characters worth knowing


`Y` `y`	2026 / 26
`m` `n`	03 / 3
`d` `j`	05 / 5
`H` `h`	24-hour / 12-hour
`i` `s`	minutes / seconds
`D` `l`	Mon / Monday
`M` `F`	Mar / March
`A`	AM or PM

#Parsing

php

$d = new DateTimeImmutable('2026-03-15');
$d = DateTimeImmutable::createFromFormat('d/m/Y', '15/03/2026');

Use createFromFormat when the input is ambiguous. 03/04/2026 is March or April depending on where you live; being explicit removes the guess.

#Differences

php

$diff = $start->diff($end);
echo $diff->days;           // total days
echo $diff->format('%a days, %h hours');

#Timezones

Store UTC in your database. Convert only for display:

php

$utc = new DateTimeImmutable($row['created_at'], new DateTimeZone('UTC'));
echo $utc->setTimezone(new DateTimeZone('America/New_York'))->format('g:i A');

Storing local times means daylight saving transitions give you an hour that happens twice and an hour that never happens.