Date and Time in PHP

Working with date and time

Almost every app shows dates — a post date, an order time, an age. PHP gives you a quick function, date(), for formatting, and a powerful class, DateTime, for calculations. Learn both and you can handle any date task.

The date() function

<?php
  date_default_timezone_set("Asia/Kolkata");
  echo date("Y-m-d");      // 2026-01-15
  echo date("H:i:s");      // 14:30:00
  echo date("l");          // Thursday
?>

The string you pass tells date() what to output. Each letter is a format code that PHP replaces with the matching part of the current date.

Common format letters

time() and timestamps

<?php
  $now = time();               // current timestamp (seconds)
  $tomorrow = $now + 86400;    // + 1 day (60*60*24)
  echo date("Y-m-d", $tomorrow);
?>

A timestamp is just a number of seconds, so adding a day means adding 86400. Pass a timestamp as the second argument to date() to format that moment.

The DateTime class

For richer work, use the object-oriented DateTime.

<?php
  $d = new DateTime("2026-01-15");
  $d->modify("+1 week");
  echo $d->format("Y-m-d");
?>

DateTime understands human phrases like "+1 week" and formats with format(), the same codes as date().

Date difference

<?php
  $d1 = new DateTime("2026-01-01");
  $d2 = new DateTime("2026-01-15");
  $diff = $d1->diff($d2);
  echo $diff->days . " days";
?>

diff() returns a DateInterval. Its ->days gives the total days between the two dates — perfect for ages, durations and deadlines.

Common mistakes

• Wrong time zone. Without setting it, times may be hours off. Set it at the top of the script.
• Mixing up format letters. m is month, M is a short month name, d is day — check the code.
• Forgetting the timestamp argument. To format a specific time, pass it as the second argument to date().
• Doing date maths by hand. Use DateTime and modify() instead of manual second counting.

Summary

• date("Y-m-d") formats the current date; letters are format codes.
• time() gives a timestamp (seconds since 1970).
• The DateTime class handles adding, comparing and formatting.
• diff() finds the gap between two dates.
• Always set the time zone for correct local times.

Next, format strings alongside dates with PHP string functions, or store dates in MySQL date types.