How to Calculate the Difference Between two Dates in PHP?

Calculating the difference between two dates is a common requirement in PHP applications. PHP provides several approaches to achieve this, from simple mathematical calculations to object-oriented methods using the DateTime class.

Using date_diff() Function

The date_diff() function calculates the difference between two DateTime objects and returns a DateInterval object representing the time difference

<?php
// Create DateTime objects
$datetime1 = date_create('2017-05-29');
$datetime2 = date_create('2023-06-20');

// Calculate the difference between DateTime objects
$interval = date_diff($datetime1, $datetime2);

// Print result in years & months format
echo $interval->format('%R%y years %m months');
?>

+6 years 0 months

Using Mathematical Formula with Timestamps

This approach converts dates to Unix timestamps and uses mathematical calculations to determine the difference in years, months, days, hours, minutes, and seconds

<?php
// Declare and define two dates
$date1 = strtotime("2020-06-01 18:36:20");
$date2 = strtotime("2023-11-23 8:25:35");

// Calculate the absolute difference
$diff = abs($date2 - $date1);

// Calculate years
$years = floor($diff / (365*60*60*24));

// Calculate months
$months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));

// Calculate days
$days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24) / (60*60*24));

// Calculate hours
$hours = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24 - $days*60*60*24) / (60*60));

// Calculate minutes
$minutes = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24 - $days*60*60*24 - $hours*60*60) / 60);

// Calculate seconds
$seconds = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24 - $days*60*60*24 - $hours*60*60 - $minutes*60));

// Print the result
printf("%d years, %d months, %d days, %d hours, %d minutes, %d seconds", 
       $years, $months, $days, $hours, $minutes, $seconds);
?>

3 years, 5 months, 24 days, 14 hours, 49 minutes, 15 seconds

Simple Day Difference Calculation

For basic day difference calculations, you can use a simple mathematical approach

<?php
// Declare two dates
$start_date = strtotime("2016-02-28");
$end_date = strtotime("2023-06-19");

// Calculate difference in days
$days_difference = ($end_date - $start_date) / 60 / 60 / 24;

echo "Difference between two dates: " . $days_difference . " days";
?>

Difference between two dates: 2668 days

Comparison

Conclusion

For accurate date calculations, use date_diff() with DateTime objects as it properly handles leap years and varying month lengths. The mathematical approach works for approximate calculations, while simple timestamp subtraction is suitable for basic day differences.