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DateTime::modify

date_modify

(PHP 5 >= 5.2.0, PHP 7)

DateTime::modify -- date_modify — Alters the timestamp

Description

Object oriented style

public DateTime::modify ( string $modify ) : DateTime

Procedural style

date_modify ( DateTime $object , string $modify ) : DateTime

Alter the timestamp of a DateTime object by incrementing or decrementing in a format accepted by strtotime().

Parameters

object: Procedural style only: A DateTime object returned by date_create(). The function modifies this object.
modify: A date/time string. Valid formats are explained in Date and Time Formats.

Return Values

Returns the DateTime object for method chaining or FALSE on failure.

Changelog

Version	Description
5.3.6	Absolute date/time statements now take effect. Previously, only relative parts were used.
5.3.0	Changed the return value on success from `NULL` to DateTime.

Examples

Example #1 DateTime::modify() example

Object oriented style


<?php
$date = new DateTime('2006-12-12');
$date->modify('+1 day');
echo $date->format('Y-m-d');
?>

Procedural style


<?php
$date = date_create('2006-12-12');
date_modify($date, '+1 day');
echo date_format($date, 'Y-m-d');
?>

The above examples will output:

2006-12-13

Example #2 Beware when adding or subtracting months


<?php
$date = new DateTime('2000-12-31');

$date->modify('+1 month');
echo $date->format('Y-m-d') . "\n";

$date->modify('+1 month');
echo $date->format('Y-m-d') . "\n";
?>

The above example will output:

2001-01-31
2001-03-03

User Contributed Notes 11 notes

down

jenspj at msn dot com ¶

7 years ago


These functions makes sure that adding months or years always ends up in the month you would expect.  Works for positive and negative values

<?php
      
       
    $date=new DateTime();
    $date->setDate(2008,2,29);
    
    function addMonths($date,$months){
         
        $init=clone $date;
        $modifier=$months.' months';
        $back_modifier =-$months.' months';
        
        $date->modify($modifier);
        $back_to_init= clone $date;
        $back_to_init->modify($back_modifier);
        
        while($init->format('m')!=$back_to_init->format('m')){
        $date->modify('-1 day')    ;
        $back_to_init= clone $date;
        $back_to_init->modify($back_modifier);    
        }
        
        /*
        if($months<0&&$date->format('m')>$init->format('m'))
        while($date->format('m')-12-$init->format('m')!=$months%12)
        $date->modify('-1 day');
        else
        if($months>0&&$date->format('m')<$init->format('m'))
        while($date->format('m')+12-$init->format('m')!=$months%12)
        $date->modify('-1 day');
        else
        while($date->format('m')-$init->format('m')!=$months%12)
        $date->modify('-1 day');
        */
        
    }
     
    function addYears($date,$years){
        
        $init=clone $date;
        $modifier=$years.' years';
        $date->modify($modifier);
        
        while($date->format('m')!=$init->format('m'))
        $date->modify('-1 day');
        
        
    } 
    
    
    
    addMonths($date,-1);
     addYears($date,3);
    
    
    echo $date->format('F j,Y');
     

?>

down

mangotonk at gmail dot com ¶

2 years ago


a slightly more compact way of getting the month shift

<?php

      /**
     * correctly calculates end of months when we shift to a shorter or longer month
     * workaround for http://php.net/manual/en/datetime.add.php#example-2489 
     * 
     * Makes the assumption that shifting from the 28th Feb +1 month is 31st March
     * Makes the assumption that shifting from the 28th Feb -1 month is 31st Jan
     * Makes the assumption that shifting from the 29,30,31 Jan +1 month is 28th (or 29th) Feb
     *
     * 
     * @param DateTime $aDate
     * @param int $months positive or negative
     * 
     * @return DateTime new instance - original parameter is unchanged
     */

    function MonthShifter (DateTime $aDate,$months){
        $dateA = clone($aDate);
        $dateB = clone($aDate);
        $plusMonths = clone($dateA->modify($months . ' Month'));
        //check whether reversing the month addition gives us the original day back
        if($dateB != $dateA->modify($months*-1 . ' Month')){ 
            $result = $plusMonths->modify('last day of last month');
        } elseif($aDate == $dateB->modify('last day of this month')){
            $result =  $plusMonths->modify('last day of this month');
        } else {
            $result = $plusMonths;
        }
        return $result;
    }

//TEST

$x = new DateTime('2017-01-30');
echo( $x->format('Y-m-d')." past end of feb, but not dec<br>");
echo('b ' . MonthShifter($x,1)->format(('Y-m-d'))."<br>");
echo('c ' . MonthShifter($x,-1)->format(('Y-m-d'))."<br>");

$x = new DateTime('2017-01-15');
echo("<br>" . $x->format('Y-m-d')." middle of the month <br>");
echo('d ' . MonthShifter($x,1)->format(('Y-m-d'))."<br>");
echo('e ' . MonthShifter($x,-1)->format(('Y-m-d'))."<br>");

$x = new DateTime('2017-02-28');
echo("<br>" . $x->format('Y-m-d')." end of Feb<br>");
echo('f ' . MonthShifter($x,1)->format(('Y-m-d'))."<br>");
echo('g ' . MonthShifter($x,-1)->format(('Y-m-d'))."<br>");

$x = new DateTime('2017-01-31');
echo("<br>" .  $x->format('Y-m-d')." end of Jan<br>");
echo('h ' . MonthShifter($x,1)->format(('Y-m-d'))."<br>");
echo('i ' . MonthShifter($x,-1)->format(('Y-m-d'))."<br>");

$x = new DateTime('2017-01-31');
echo("<br>" .  $x->format('Y-m-d')." end of Jan +/- 1 years diff, leap year respected<br>");
echo('j ' . MonthShifter($x,13)->format(('Y-m-d'))."<br>");
echo('k ' . MonthShifter($x,-11)->format(('Y-m-d'))."<br>");

//returns

2017-01-30 past end of feb, but not dec
b 2017-02-28
c 2016-12-30

2017-01-15 middle of the month 
d 2017-02-15
e 2016-12-15

2017-02-28end of Feb
f 2017-03-31
g 2017-01-31

2017-01-31end of Jan
h 2017-02-28
i 2016-12-31

2017-01-31end of Jan +/- 1 years diff, leap year respected
j 2018-02-28
k 2016-02-29

down

www dot wesley at gmail dot com ¶

4 years ago


This is an improvement of @jenspj's answer

<?php

$d = new DateTime('2007-12-31');

function addMonths($date, $months)
{
    $years = floor(abs($months / 12));
    $leap = 29 <= $date->format('d');
    $m = 12 * (0 <= $months?1:-1);
    for ($a = 1;$a < $years;++$a) {
        $date = addMonths($date, $m);
    }
    $months -= ($a - 1) * $m;
    
    $init = clone $date;
    if (0 != $months) {
        $modifier = $months . ' months';
        
        $date->modify($modifier);
        if ($date->format('m') % 12 != (12 + $months + $init->format('m')) % 12) {
            $day = $date->format('d');
            $init->modify("-{$day} days");
        }
        $init->modify($modifier);
    }
    
    $y = $init->format('Y');
    if ($leap && ($y % 4) == 0 && ($y % 100) != 0 && 28 == $init->format('d')) {
        $init->modify('+1 day');
    }
    return $init;
}

function addYears($date, $years)
{
    return addMonths($date, 12 * $years);
}

echo $d->format('F j,Y') . ' N<br />';
$d = addMonths($d, +1);
echo $d->format('F j,Y') . ' +1M<br />';
$d = addMonths($d, +1);
echo $d->format('F j,Y') . ' +1M<br />';
$d = addYears($d, +60);
echo $d->format('F j,Y') . ' +60Y<br />';
$d = addYears($d, -59);
echo $d->format('F j,Y') . ' -59Y<br />';

down

jay dot removethis at grooveshark dot com ¶

5 years ago


Due to DST and the way DateTime internally handles dates, it's possible to get stuck in a time loop.

For example:

<?php
$dt = new DateTime('2012-03-11 3:00AM');
echo $dt->format('YmdH') . "\n";
$dt->modify("-1 hour");
echo $dt->format('YmdH') . "\n";
$dt->modify("-1 hour");
echo $dt->format('YmdH') . "\n";
?>

prints out:

2012031103
2012031103
2012031103

if your timezone is set to America/New_York.

down

vittorio dot zamparella at gmail dot com ¶

7 months ago


@Anonimous 
There is no bug. Especially not any retarded one.

<? 
function plusOneMonthTests($dateString, $expectation) {
    $date = new DateTime($dateString);
    echo "[".$date->format('Y-m-d')."] +1 month = [".$date->modify('+1 month')->format('Y-m-d')."] $expectation \n";
}    
plusOneMonthTests('2001-01-01', 'as expected');
plusOneMonthTests('2001-01-27', 'as expected');
plusOneMonthTests('2001-01-28', 'as expected');
plusOneMonthTests('2001-01-29', 'what would you expect?');
plusOneMonthTests('2001-01-30', 'what would you expect?');
plusOneMonthTests('2001-01-31', 'what would you expect?');
?>
Result: 
[2001-01-01] +1 month = [2001-02-01] as expected 
[2001-01-27] +1 month = [2001-02-27] as expected 
[2001-01-28] +1 month = [2001-02-28] as expected 
[2001-01-29] +1 month = [2001-03-01] what would you expect? 29 of february??
[2001-01-30] +1 month = [2001-03-02] what would you expect? or 30 of february?
[2001-01-31] +1 month = [2001-03-03] what would you expect? 

As with any tool you need to know how to use it. 

I think most people are looking for "the same day of the next month" (or any other number or months). 

The calendar is twisted, don't blame the library.

down

66Ton99 ¶

5 years ago


Extension for DateTime class which solves problem of adding or subtracting months

https://gist.github.com/66Ton99/60571ee49bf1906aaa1c

down

sinus at sinpi dot net ¶

2 years ago


A very simple way to ensure we do not cross over month boundaries when adding months is to just go back a few days if the day number got reset:

<?php
function addMonths($date,$months) {
  $orig_day = $date->format("d");
  $date->modify("+".$months." months");
  while ($date->format("d")<$orig_day && $date->format("d")<5) {
    $date->modify("-1 day");
  }
}

for ($i=0;$i<5;$i++) {
  $d = new DateTime("2000-01-10");
  addmonths($d,$i);
  echo $d->format("Y-m-d")."<br>";
}
for ($i=0;$i<5;$i++) {
  $d = new DateTime("2000-01-31");
  addmonths($d,$i);
  echo $d->format("Y-m-d")."<br>";
}
?>

prints:
2000-01-10
2000-02-10
2000-03-10
2000-04-10
2000-05-10
2000-01-31
2000-02-29
2000-03-31
2000-04-30
2000-05-31

down

Jenny jsimonds@atomic jet packs dot com ¶

7 years ago


Note: This method modifies the object in-place. So if you want to calculate a new date but assign the new value to a different object, this will NOT work:

<?php
$numMinutes = 25;
$oDateA = new DateTime('2012-01-01 12:00:00');

print "
Original:<br>
oDateA =  {$oDateA->format('Y-m-d H-i-s')}<br>
";

$oDateB = $oDateA->modify ("+{$numMinutes} minutes");

print "
plus {$numMinutes} minutes:<br>
oDateA =  {$oDateA->format('Y-m-d H-i-s')}<br>
oDateB =  {$oDateB->format('Y-m-d H-i-s')}<br>
";
?>
...produces this:
oDateA = 2012-01-01 12-00-00
plus 25 minutes:
oDateA = 2012-01-01 12-25-00
oDateB = 2012-01-01 12-25-00

Use something like this instead:
<?php
$numMinutes = 25;
$oDateA = new DateTime('2012-01-01 12:00:00');

print "
<p>
Original:<br>
oDateA =  {$oDateA->format('Y-m-d H-i-s')}<br>
";

$oDateB = clone $oDateA;
$oDateB->modify ("+{$numMinutes} minutes");

print "
plus {$numMinutes} minutes:<br>
oDateA =  {$oDateA->format('Y-m-d H-i-s')}<br>
oDateB =  {$oDateB->format('Y-m-d H-i-s')}<br>
";
?>

... produces this:
oDateA = 2012-01-01 12-00-00
plus 25 minutes:
oDateA = 2012-01-01 12-00-00
oDateB = 2012-01-01 12-25-00

down

php at lanar dot com dot au ¶

5 years ago


modify() ignores any timezone information in the data while the DateTime constructor does not.

$dt = new DateTime( '2013-10-26T11:00:00+11:00' ) 
will create a +11 timezone while
$dt->modify( '2013-10-26T11:00:00+02:00' )
does not change the timezone or the time.

<?php
$dt = new DateTime( '2013-10-26T15:00:00Australia/Melbourne' ) ;
echo "\n", $dt->format( "c" ) ;
echo "\nTimezone '", $dt->getTimezone()->getName() . "'." ;
// modify $dt to 1 am new york which is 3 pm melbourne
$dt->modify( '2013-10-26T01:00:00America/New_York' ) ;
// result is 1 am melbourne time, not 3 pm
echo "\n", $dt->format( "c" ) ;
echo "\nTimezone '", $dt->getTimezone()->getName() . "'." ;
?>
Output
2013-10-26T15:00:00+11:00
Timezone 'Australia/Melbourne'.
2013-10-26T01:00:00+11:00
Timezone 'Australia/Melbourne'.

down

ilyaplot at gmail dot com ¶

1 year ago


function subMonths(\Datetime $dateTime, int $months)
{
    if ($invert = $months < 0) {
        $months *= -1;
    }

    for ($i=0; $i<$months; $i++) {
        $daysOfMonth = cal_days_in_month(CAL_GREGORIAN, $dateTime->format('m'), $dateTime->format('Y'));
        $dateTime->modify(($invert ? '-' : '+') . $daysOfMonth . ' day');
    }
    return $dateTime;
}

$dateTime = new \DateTime('2004-12-31');

echo $dateTime->modify('-3 month')->format('Y-m-d'); // 2004-10-01

echo subMonths($dateTime, -3)->format('Y-m-d'); // 2004-09-30

down

-1

admin at wmfoi dot com dot br ¶

5 years ago


The changelog says: "5.3.0 - Changed the return value on success from NULL to DateTime".

That means that you can't do a Fluid Interface design with it in PHP 5.2.

In other words, this will not work in 5.2:

<?php
$DateTime=new DateTime();
echo $DateTime->modify('+1 day')->format('d');
?>

add a note

DateTime::modify

date_modify

Description

Parameters

Return Values

Changelog

Examples

See Also

User Contributed Notes 11 notes