How to calculate the difference between two dates using PHP?
I have two dates of the form:
Start Date: 2007-03-24
End Date: 2009-06-26
Now I need to find the difference between these two in the following form:
2 years, 3 months and 2 days
How can I do this in PHP?
For PHP < 5.3 otherwise see jurka's answer below
You can use strtotime() to convert two dates to unix time and then calculate the number of seconds between them. From this it's rather easy to calculate different time periods.
$date1 = "2007-03-24";
$date2 = "2009-06-26";
$diff = abs(strtotime($date2) - strtotime($date1));
$years = floor($diff / (365*60*60*24));
$months = floor(($diff - $years * 365*60*60*24) / (30*60*60*24));
$days = floor(($diff - $years * 365*60*60*24 - $months*30*60*60*24)/ (60*60*24));
printf("%d years, %d months, %d daysn", $years, $months, $days);
Edit: Obviously the preferred way of doing this is like described by jurka below. My code is generally only recommended if you don't have PHP 5.3 or better.
Several people in the comments have pointed out that the code above is only an approximation. I still believe that for most purposes that's fine, since the usage of a range is more to provide a sense of how much time has passed or remains rather than to provide precision - if you want to do that, just output the date.
Despite all that, I've decided to address the complaints. If you truly need an exact range but haven't got access to PHP 5.3, use the code below (it should work in PHP 4 as well). This is a direct port of the code that PHP uses internally to calculate ranges, with the exception that it doesn't take daylight savings time into account. That means that it's off by an hour at most, but except for that it should be correct.
<?php
/**
* Calculate differences between two dates with precise semantics. Based on PHPs DateTime::diff()
* implementation by Derick Rethans. Ported to PHP by Emil H, 2011-05-02. No rights reserved.
*
* See here for original code:
* http://svn.php.net/viewvc/php/php-src/trunk/ext/date/lib/tm2unixtime.c?revision=302890&view=markup
* http://svn.php.net/viewvc/php/php-src/trunk/ext/date/lib/interval.c?revision=298973&view=markup
*/
function _date_range_limit($start, $end, $adj, $a, $b, $result)
{
if ($result[$a] < $start) {
$result[$b] -= intval(($start - $result[$a] - 1) / $adj) + 1;
$result[$a] += $adj * intval(($start - $result[$a] - 1) / $adj + 1);
}
if ($result[$a] >= $end) {
$result[$b] += intval($result[$a] / $adj);
$result[$a] -= $adj * intval($result[$a] / $adj);
}
return $result;
}
function _date_range_limit_days($base, $result)
{
$days_in_month_leap = array(31, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
$days_in_month = array(31, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
_date_range_limit(1, 13, 12, "m", "y", &$base);
$year = $base["y"];
$month = $base["m"];
if (!$result["invert"]) {
while ($result["d"] < 0) {
$month--;
if ($month < 1) {
$month += 12;
$year--;
}
$leapyear = $year % 400 == 0 || ($year % 100 != 0 && $year % 4 == 0);
$days = $leapyear ? $days_in_month_leap[$month] : $days_in_month[$month];
$result["d"] += $days;
$result["m"]--;
}
} else {
while ($result["d"] < 0) {
$leapyear = $year % 400 == 0 || ($year % 100 != 0 && $year % 4 == 0);
$days = $leapyear ? $days_in_month_leap[$month] : $days_in_month[$month];
$result["d"] += $days;
$result["m"]--;
$month++;
if ($month > 12) {
$month -= 12;
$year++;
}
}
}
return $result;
}
function _date_normalize($base, $result)
{
$result = _date_range_limit(0, 60, 60, "s", "i", $result);
$result = _date_range_limit(0, 60, 60, "i", "h", $result);
$result = _date_range_limit(0, 24, 24, "h", "d", $result);
$result = _date_range_limit(0, 12, 12, "m", "y", $result);
$result = _date_range_limit_days(&$base, &$result);
$result = _date_range_limit(0, 12, 12, "m", "y", $result);
return $result;
}
/**
* Accepts two unix timestamps.
*/
function _date_diff($one, $two)
{
$invert = false;
if ($one > $two) {
list($one, $two) = array($two, $one);
$invert = true;
}
$key = array("y", "m", "d", "h", "i", "s");
$a = array_combine($key, array_map("intval", explode(" ", date("Y m d H i s", $one))));
$b = array_combine($key, array_map("intval", explode(" ", date("Y m d H i s", $two))));
$result = array();
$result["y"] = $b["y"] - $a["y"];
$result["m"] = $b["m"] - $a["m"];
$result["d"] = $b["d"] - $a["d"];
$result["h"] = $b["h"] - $a["h"];
$result["i"] = $b["i"] - $a["i"];
$result["s"] = $b["s"] - $a["s"];
$result["invert"] = $invert ? 1 : 0;
$result["days"] = intval(abs(($one - $two)/86400));
if ($invert) {
_date_normalize(&$a, &$result);
} else {
_date_normalize(&$b, &$result);
}
return $result;
}
$date = "1986-11-10 19:37:22";
print_r(_date_diff(strtotime($date), time()));
print_r(_date_diff(time(), strtotime($date)));
I suggest to use DateTime and DateInterval objects.
$date1 = new DateTime("2007-03-24");
$date2 = new DateTime("2009-06-26");
$interval = $date1->diff($date2);
echo "difference " . $interval->y . " years, " . $interval->m." months, ".$interval->d." days ";
// shows the total amount of days (not divided into years, months and days like above)
echo "difference " . $interval->days . " days ";
read more php DateTime::diff manual
From the manual:
As of PHP 5.2.2, DateTime objects can be compared using comparison operators.
$date1 = new DateTime("now");
$date2 = new DateTime("tomorrow");
var_dump($date1 == $date2); // bool(false)
var_dump($date1 < $date2); // bool(true)
var_dump($date1 > $date2); // bool(false)
The best course of action is using PHP's DateTime (and DateInterval ) objects. Each date is encapsulated in a DateTime object, and then a difference between the two can be made:
$first_date = new DateTime("2012-11-30 17:03:30");
$second_date = new DateTime("2012-12-21 00:00:00");
The DateTime object will accept any format strtotime() would. If an even more specific date format is needed, DateTime::createFromFormat() can be used to create the DateTime object.
After both objects were instantiated, you substract one from the other with DateTime::diff() .
$difference = $first_date->diff($second_date);
$difference now holds a DateInterval object with the difference information. A var_dump() looks like this:
object(DateInterval)
public 'y' => int 0
public 'm' => int 0
public 'd' => int 20
public 'h' => int 6
public 'i' => int 56
public 's' => int 30
public 'invert' => int 0
public 'days' => int 20
To format the DateInterval object, we'll need check each value and exclude it if it's 0:
/**
* Format an interval to show all existing components.
* If the interval doesn't have a time component (years, months, etc)
* That component won't be displayed.
*
* @param DateInterval $interval The interval
*
* @return string Formatted interval string.
*/
function format_interval(DateInterval $interval) {
$result = "";
if ($interval->y) { $result .= $interval->format("%y years "); }
if ($interval->m) { $result .= $interval->format("%m months "); }
if ($interval->d) { $result .= $interval->format("%d days "); }
if ($interval->h) { $result .= $interval->format("%h hours "); }
if ($interval->i) { $result .= $interval->format("%i minutes "); }
if ($interval->s) { $result .= $interval->format("%s seconds "); }
return $result;
}
All that's left now is to call our function on the $difference DateInterval object:
echo format_interval($difference);
And we get the correct result:
20 days 6 hours 56 minutes 30 seconds
The complete code used to achieve the goal:
/**
* Format an interval to show all existing components.
* If the interval doesn't have a time component (years, months, etc)
* That component won't be displayed.
*
* @param DateInterval $interval The interval
*
* @return string Formatted interval string.
*/
function format_interval(DateInterval $interval) {
$result = "";
if ($interval->y) { $result .= $interval->format("%y years "); }
if ($interval->m) { $result .= $interval->format("%m months "); }
if ($interval->d) { $result .= $interval->format("%d days "); }
if ($interval->h) { $result .= $interval->format("%h hours "); }
if ($interval->i) { $result .= $interval->format("%i minutes "); }
if ($interval->s) { $result .= $interval->format("%s seconds "); }
return $result;
}
$first_date = new DateTime("2012-11-30 17:03:30");
$second_date = new DateTime("2012-12-21 00:00:00");
$difference = $first_date->diff($second_date);
echo format_interval($difference);
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