How to Calculate Time Between Two Dates in PHP

PHP has a variety of functions and formats for working with dates and times.

PHP is a general-purpose server-side scripting language that was originally designed for creating dynamic Web pages. PHP is an open-source language that can be configured to run on UNIX, Linux, Windows or Mac OSX, supports a wide range of databases and has a comprehensive library of built-in extensions. The PHP core installation contains many date and time functions and formats that can be used and manipulated by those creating dynamic Web pages, writing server scripts or coding stand-alone applications.

Things You'll Need

• Text editor
• Web server with PHP 5 or later installed and configured
• Web browser

Instructions

1. Open a text editor and create a new file named timeBetweenDates.php. Save the file on a Web server in a location that has access to PHP.

2. Edit timeBetweenDates.php. Type a <?PHP PHP open tag and a ?> PHP close tag in the file. When the PHP program parses the file, it will consider text placed between these two tags code.

   <?PHP

   ?>

3. Use the PHP date_default_timezone_set() function to set the server's time zone to America/New_York. The time zone will be set for the duration of the script.

   <?PHP

   date_default_timezone_set('America/New_York');

   ?>

4. Declare a variable named $start_date and use the strtotime() PHP date/time function to parse the date/time into a UNIX time stamp relative to now. Use the date July 30, 1970, or 7/30/1970.

   <?PHP

   date_default_timezone_set('America/New_York');

   $start_date = strtotime('7/30/1970');

   ?>

5. Declare a variable named $end_date and use the strtotime() PHP date/time function to parse the date/time into a UNIX time stamp relative to now. Use the date July 30, 2011, or 7/30/2011.

   <?PHP

   date_default_timezone_set('America/New_York');

   $start_date = strtotime('7/30/1970');

   $end_date = strtotime('7/30/2011');

   ?>

6. Declare a variable named $years_between_dates to hold the result of the date calculation. Use the abs() function to subtract the $end_date variable from the $start_date variable and divide the result by 86400 (the number of seconds in a day). The $years_between_dates variable now holds the number of days that have passed between $start_date and $end_date.

   <?PHP

   date_default_timezone_set('America/New_York');

   $start_date = strtotime('7/30/1970');

   $end_date = strtotime('7/30/2011');

   $years_between_dates = abs(($start_date-$end_date)/86400);

   ?>

7. Use the round() function to divide the $years_between_dates variable by 365 (the number of days in a year) rounded to the closest year. Store the result back in the $years_between_dates variable.

   <?PHP

   date_default_timezone_set('America/New_York');

   $start_date = strtotime('7/30/1970');

   $end_date = strtotime('7/30/2011');

   $years_between_dates = abs(($start_date-$end_date)/86400);

   $years_between_dates = round($years_between_dates/365);

   ?>

8. Use the PHP echo() command to write the text "The number of years between the two dates is: " to the Web page. Concatenate the text with the variable $years_between_dates using the PHP concatenation operator (a period). Save and close timeBetweenDates.php.

   <?PHP

   date_default_timezone_set('America/New_York');

   $start_date = strtotime('7/30/1970');

   $end_date = strtotime('7/30/2011');

   $years_between_dates = abs(($start_date-$end_date)/86400);

   $years_between_dates = round($years_between_dates/365);

   echo "The number of years between the two dates is: " . $years_between_dates;

   ?>

9. Open a Web browser and request timeBetweenDates.php from the Web server. The difference between the two dates will be displayed in years.

Tips & Warnings

• Dozens of time zone values are available to you when you are setting the default time zone used in date/time functions. See the Resources section for a comprehensive list.

• PHP date/time functions are part of PHP core and do not require a separate installation.

• PHP date/time functions are dependent on server settings and may be set in php.ini.

• The strtotime() function can parse many date/time formats, including relative dates, such as "next Saturday" or "+7 hours."

• The date_default_timezone_set function is available in PHP 5 and up.

References

• The PHP Group: Date/Time Functions: strotime
• The PHP Group: What can PHP do?
• W3Schools.com: PHP strtotime() Function

Resources

• The PHP Group: List of supported timezones