Madison PHP Conference 2017


(PHP 5 >= 5.3.0)

DateInterval::__constructCreates new DateInterval object


public DateInterval::__construct() ( string $interval_spec )

Creates new DateInterval object.



Interval specification.

The format starts with the letter P, for "period." Each duration period is represented by an integer value followed by a period designator. If the duration contains time elements, that portion of the specification is preceded by the letter T.

interval_spec Period Designators
Period Designator Description
Y years
M months
D days
W weeks. These get converted into days, so can not be combined with D.
H hours
M minutes
S seconds

Here are some simple examples. Two days is P2D. Two seconds is PT2S. Six years and five minutes is P6YT5M.


The unit types must be entered from the largest scale unit on the left to the smallest scale unit on the right. So years before months, months before days, days before minutes, etc. Thus one year and four days must be represented as P1Y4D, not P4D1Y.

The specification can also be represented as a date time. A sample of one year and four days would be P0001-00-04T00:00:00. But the values in this format can not exceed a given period's roll-over-point (e.g. 25 hours is invalid).

These formats are based on the » ISO 8601 duration specification.


Example #1 DateInterval example


= new DateInterval('P2Y4DT6H8M');


The above example will output:

DateInterval Object
    [y] => 2
    [m] => 0
    [d] => 4
    [h] => 6
    [i] => 8
    [s] => 0
    [invert] => 0
    [days] => 0

See Also

  • DateInterval::format() - Formats the interval
  • DateTime::add() - اصافه کردن تعداد روز، ماه، سال، ساعت، دقیقه و ثانیه به شی DateTime
  • DateTime::sub() - کم کردن تعدادی روز، ماه، سال، ساعت، دقیقه و ثانیه به شی DateTime
  • DateTime::diff() - بازگرداندن تفاوت بین دو شی DateTime

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User Contributed Notes 11 notes

owen at
3 years ago
M is used to indicate both months and minutes.

As noted on the referenced wikipedia page for ISO 6801

To resolve ambiguity, "P1M" is a one-month duration and "PT1M" is a one-minute duration (note the time designator, T, that precedes the time value).

Using: PHP 5.3.2-1ubuntu4.19

// For 3 Months
$dateTime = new DateTime;echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
$dateTime->add(new DateInterval("P3M"));
echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
Results in:

// For 3 Minutes
$dateTime = new DateTime;echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
$dateTime->add(new DateInterval("PT3M"));
echo $dateTime->format( DateTime::ISO8601 ), PHP_EOL;
Results in:

Insert a T after the P in the interval to add 3 minutes instead of 3 months.
kevinpeno at gmail dot com
5 years ago
Note that, while a DateInterval object has an $invert property, you cannot supply a negative directly to the constructor similar to specifying a negative in XSD ("-P1Y"). You will get an exception through if you do this.

Instead you need to construct using a positive interval ("P1Y") and the specify the $invert property === 1.
admin at torntech dot com
2 years ago
Warning - despite the $interval_spec accepting the ISO 8601 specification format, it does not accept decimal fraction values with period or comma as stated in the specification.

/* Example from ISO 8601 documentation */
$interval = new DateInterval('P0.5Y');

Will result in
Fatal error: Uncaught exception 'Exception' with message 'DateInterval::__construct(): Unknown or bad format (P0.5Y)'
buvinghausen at gmail dot com
4 years ago
I think it is easiest if you would just use the sub method on the DateTime class.

= new DateTime();
$date->sub(new DateInterval("P89D"));
userexamplecom at mailinator dot com
1 year ago
Take care, if you have a DateTime Object on the 31h of January and add Da DateInterval of one Month, then you are in March instead of February.

For Example:
// given the actual date is 2017-01-31
$today = new DateTime('now', $timeZoneObject);
$today->add(new DateInterval('P1M'));
echo $today->format('m');
// output: 03
daniellehr at gmx dot de
4 years ago
Alternatively you can use DateInterval::createFromDateString() for negative intervals:

= new DateTime();
$date->add(DateInterval::createFromDateString('-89 days'));
lsloan-php dot net at umich dot edu
11 months ago
Although PHP refers to periods of time as "intervals", ISO 8601 refers to them as "durations".  In ISO 8601, "intervals" are something else.

While ISO 8601 allows fractions for all parts of a duration (e.g., "P0.5Y"), DateInterval does not.  Use caution when calculating durations.  If the duration has a fractional part, it may be lost when storing it in a DateInterval object.
6 years ago
It should be noted that this class will not calculate days/hours/minutes/seconds etc given a value in a single denomination of time.  For example:

= new DateInterval('PT3600S');

will yield 0:0:3600 instead of the expected 1:0:0
jawzx01 at gmail dot com
5 years ago
As previously mentioned, to do a negative DateInterval object, you'd code:

= new DateTime();
$eightynine_days_ago = new DateInterval( "P89D" );
$eightynine_days_ago->invert = 1; //Make it negative.
$date1->add( $eightynine_days_ago );

and then $date1 is now 89 days in the past.
Ray.Paseur sometimes uses Gmail
10 months ago
To recover the interval specification string:

function get_interval_spec(DateTime $alpha, DateTime $omega)
$intvl = $alpha->diff($omega);

$date = NULL;
    if (
$intvl->y) $date .= $intvl->y . 'Y';
    if (
$intvl->m) $date .= $intvl->m . 'M';
    if (
$intvl->d) $date .= $intvl->d . 'D';

$time = NULL;
    if (
$intvl->h) $time .= $intvl->h . 'H';
    if (
$intvl->i) $time .= $intvl->i . 'M';
    if (
$intvl->s) $time .= $intvl->s . 'S';
    if (
$time) $time = 'T' . $time;

$text ='P' . $date . $time;
    if (
$text == 'P') return 'PT0S';
bkilinc at deyta dot net
3 years ago
interval_spec Period Designators, has two 'M's for months and minutes.
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