PHP time

Summary: in this tutorial, you’ll learn how to work with the PHP time() function to get the current timestamp in the local timezone.

Introduction to Unix timestamps

Computers store a date and time as a UNIX timestamp or a timestamp in short.

A timestamp is an integer that refers to the number of seconds between 1970-01-01 00:00:00 UTC (Epoch) and the date and time to be stored.

Computers store dates and times as timestamps because it is easier to manipulate an integer. For example, to add one day to a timestamp, it simply adds the number of seconds to the timestamp.

PHP provides some helpful functions that manipulate timestamps effectively.

Getting the current time

To get the current time, you use the time() function:

function time(): int
Code language: PHP (php)

The time() function returns the current UNIX timestamp since Epoch (January 1 1970 00:00:00 GMT). For example:

<?php echo time(); // 1626752728
Code language: PHP (php)

The return value is a big integer that represents the number of seconds since Epoch. To make the time human-readable, you use the date() function. For example:

<?php $current_time = time(); echo date('Y-m-d g:ia', $current_time) . '<br>';
Code language: PHP (php)

Output:

2021-07-13 5:47am
Code language: PHP (php)

The date() function has two parameters.

Since the time() function returns a timestamp, you can add seconds to it.

Adding to / subtracting from a timestamp

The following example shows how to add a week to the current time:

<?php $current_time = time(); // 7 days later $one_week_later = $current_time + 7 * 24 * 60 * 60; echo date('Y-m-d g:ia',$one_week_later);
Code language: PHP (php)

In this example, we add 7 days * 24 hours * 60 minutes * 60 seconds to the current time.

Also, you can represent a time in the past by subtracting a number of seconds from the current time. For example:

<?php $current_time = time(); // 1 day ago $yesterday = $current_time - 24 * 60 * 60; echo date('Y-m-d g:ia',$yesterday);
Code language: PHP (php)

timezone

By default, the time() function returns the current time in the timezone specified in the PHP configuration file (php.ini).

To get the current timezone, you can use the date_default_timezone_get() function:

<?php echo echo date_default_timezone_get();
Code language: PHP (php)

To set a specific timezone, you use the date_default_timezone_set(). It’s recommended that you use the UTC timezone.

The following shows how to use the date_default_timezone_set() function to set the current timezone to the UTC timezone:

<?php date_default_timezone_set('UTC');
Code language: PHP (php)

Making a Unix timestamp

To make a Unix timestamp, you use the mktime() function:

mktime( int $hour, int|null $minute = null, int|null $second = null, int|null $month = null, int|null $day = null, int|null $year = null ): int|false
Code language: PHP (php)

The mktime() function returns a Unix timestamp based on its arguments. If you omit an argument, mktime() function will use the current value according to the local date and time instead.

The following example shows how to use the mktime() function to show that July 13, 2020, is on a Tuesday:

<?php echo 'July 13, 2021 is on a ' . date('l', mktime(0, 0, 0, 7, 13, 2021));
Code language: PHP (php)

Summary

  • Use the time() function to return the current timestamp since Epoch in local timezone.
  • Use the date_default_timezone_set() function to set a specific timezone.
  • Use the date() function to format the timestamp.
  • Use mktime() function to create a timestasmp based on the year, month, day, hour, minute, and second.
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