PHP - Manipulate dates

By xngo on August 4, 2019

PHP provides DateTime and DateInterval classes to make it easier to manipulate dates. Examples below show how to edit, add, subtract and get difference between dates.

Set dates

<?php
 
// Create an instance of the current date & time.
$dt = new DateTime();
 
// Set $dt to a specific date.
$dt->setDate(2019, 8, 4);   
echo $dt->format('Y-m-d\TH:i:s.u') . "\n";
 
// modify() uses the same format as strtotime().
$dt->modify('+ 7 days');
echo $dt->format('c') . "\n";
 
$dt->modify('next month');
echo $dt->format('c') . "\n";
 
$dt->modify('last day of this month');
echo $dt->format('c') . "\n";
 
?>

Output

2019-08-04T14:46:52.113419
2019-08-11T14:46:52-04:00
2019-09-11T14:46:52-04:00
2019-09-30T14:46:52-04:00

Add / subtract time from date

DateTime class provides add() and sub() methods to add and subtract time from date. They require a DateInterval object containing the amount of time to add or to subtract from the date. The amount of time is set as a text string. It follows the following format. It starts with the character P to define the interval as a period and followed by the amount of years, months, days, hours, minutes, seconds that you want. For example, an interval string for a period of 2 years, 3 months, 4 days, 5 hours, 6 minutes and 7 seconds is P2Y3M4DT5H6M7S. Note: Before you define time values, you have to prefix with the T character.

<?php
 
// Create an instance of the current date & time.
$dt = new DateTime();
$dt->setDate(2019, 8, 4);
$dt->setTime(0, 0, 0);   
 
// Add interval period.
$interval = "P3D"; // A period of 3 days.
$dt->add( new DateInterval($interval) );
echo $dt->format('c') . "\n";
 
// Add a period of 2years, 3months, 4days, 5hours, 6min, 7sec.
$interval = "P2Y3M4DT5H6M7S"; // Prefix 'T' before time values.
$dt->add( new DateInterval($interval) );
echo $dt->format('c') . "\n";
 
// subtract interval period.
$interval = "P1Y"; // subtract 1 year.
$dt->sub( new DateInterval($interval) );
echo $dt->format('c') . "\n";
 
?>

Output

2019-08-07T00:00:00-04:00
2021-11-11T05:06:07-05:00
2020-11-11T05:06:07-05:00

Get difference between dates

DateTime class provides a neat method called diff() to get the difference between 2 dates. It returns a DateInterval object which contains the breakdown of the difference in years, months, days, hours, minutes, seconds, etc. Here is an example below.

<?php
 
// 1st date.
$dt_1 = new DateTime();
$dt_1->setDate(2019, 8, 23);
$dt_1->setTime(6, 7, 8);   
 
// 2nd date.
$dt_2 = new DateTime();
$dt_2->setDate(2017, 6, 7);
$dt_2->setTime(0, 0, 0);   
 
// Get difference between dates.
$diff = $dt_2->diff($dt_1);
print_r( $diff );
print($diff->days);
?>

Output

DateInterval Object
(
    [y] => 2
    [m] => 2
    [d] => 16
    [h] => 6
    [i] => 7
    [s] => 8
    [f] => 0
    [weekday] => 0
    [weekday_behavior] => 0
    [first_last_day_of] => 0
    [invert] => 0
    [days] => 807
    [special_type] => 0
    [special_amount] => 0
    [have_weekday_relative] => 0
    [have_special_relative] => 0
)
807
PHP

About the author

Xuan Ngo is the founder of OpenWritings.net. He currently lives in Montreal, Canada. He loves to write about programming and open source subjects.