PHP Thinks There is 6 Days When There is 7

[spoondevil]

Doing a date difference between 24th March 2008 and 31st March 2008.

If you look on a calendar, then there are 7 days between the 2 dates.

Do it through a standard PHP timestamp sum and it only shows 6 days.

Here's the script:

$d1=mktime(0,0,0,03,24,2008);
$d2=mktime(0,0,0,03,31,2008);
number_days = floor(($d2-$d1)/86400); 

It actually shows 6.9583333333333 if I don't put the floor() in, but I need that in for other days.

Anyone else come across this problem?

Ian

[r937]

If you look on a calendar, then there are 7 days between the 2 dates.

no, that's not true

between the 24th and 31st are only the 25th, 26th, 27th, 28th, 29th, and 30th

six

[spoondevil]

no, that's not true

between the 24th and 31st are only the 25th, 26th, 27th, 28th, 29th, and 30th

six

LOL, you got me on that one...

What I should've said was between 00:00:00AM on the 24th March 2008 and 00:00:00AM on the 31st March 2008 there are 168 hours which breaks down to 7 days, but PHP is only recognising it as 6.95 days which throws my query into the ground

[Wildhoney]

r937 is spot on. However, you may use ceil() to make that 6 go up to 7 if you insist there is 7 days.

[r937]

just out of curiosity, would you kindly echo the values you get for $d1 and $d2

[Ickmund]

I have come across this before, twice. The first time I din't know what happend (was in march), and I couldn't duplicate the problem.

Next time it happend thou, I dug a little deeper. Has to do with daylight savings time, DST. Check out php.net/mktime for more info.

[jagat_21]

just out of curiosity, would you kindly echo the values you get for $d1 and $d2

Following is the output :

1206297000 <== D1 Value
1206901800 <== D2 Value
7 <== No. Of days.

[r937]

well, i don't have php, so i ran those dates through the mysql UNIX_TIMESTAMP function, and i got two completely different values!!!!

2008-03-31 = 1206936000
2008-03-24 = 1206331200

difference = 604800 seconds = 7.0 days exactly

[jagat_21]

Hi,

this might help u. Check it if suits ur requirement.....

/* Function For Date Difference */ 
	function dateDiff($dformat, $endDate, $beginDate)
	{
		$date_parts1=explode($dformat, $beginDate);
		$date_parts2=explode($dformat, $endDate);
		$start_date=gregoriantojd($date_parts1[0], $date_parts1[1], $date_parts1[2]);
		$end_date=gregoriantojd($date_parts2[0], $date_parts2[1], $date_parts2[2]);
		return $end_date - $start_date;
	}
    $date1="03/24/2008"; 
    $date2="03/31/2008";
    print "If we minus " . $date1 . " from " . $date2 . " we get " . dateDiff("/", $date2, $date1) . ".";

Will generate following output :

If we minus 03/24/2008 from 03/31/2008 we get 7.

[spoondevil]

just out of curiosity, would you kindly echo the values you get for $d1 and $d2

$d1=1206316800
$d2=1206918000 

[cranial-bore]

Off Topic:

well, i don't have php, so i....

No wonder you do all your date formatting in MySQL then

[r937]

Off Topic:

actually, no -- i do all my date formatting in ColdFusion

[spoondevil]

Next time it happend thou, I dug a little deeper. Has to do with daylight savings time, DST. Check out php.net/mktime for more info.

This sounds like the logical explanation as the BST +1hr comes in on the 25th March in 2008, so it might be that that's throwing a spanner into the works.

But, as the date of BST changing every year as it's always on a Saturday night rather than a specific date, I think I'm gonna have to go with jagat_21's code as that seems to work no matter what year/date you are looking at.

[lkagan]

jagat_21's code is a solution I haven't seen before and a good one at that. As for the people that didn't know about the conversion functions jagat_21 used (like myself), we could use PEAR's Date and Date_Span.

[logic_earth]

strtotime is your friend.
http://www.php.net/manual/en/function.strtotime.php

<?php

$date = '03/24/2008';

$dA = strtotime($date);
$dB = strtotime($date . ' +7Days');

var_dump($dA);
var_dump($dB);

var_dump(date('F j, Y', $dA));
var_dump(date('F j, Y', $dB)); // 03/31/2008
// n

Edit:
Also found this.

$d1 = strtotime('03/24/2008');
$d2 = strtotime('03/31/2008');

echo 'Hours difference = '   . floor(($d2 - $d1) / 3600) . '<br>';
echo 'Minutes difference = ' . floor(($d2 - $d1) / 60)   . '<br>';
echo 'Seconds difference = ' . ($d2 - $d1)               . '<br>';

echo 'Month difference = ' . floor(($d2 - $d1) / 2628000)  . '<br>';
echo 'Days difference = '  . floor(($d2 - $d1) / 86400)    . '<br>';
echo 'Year difference = '  . floor(($d2 - $d1) / 31536000) . '<br>'; 

returns:

Hours difference = 168
Minutes difference = 10080
Seconds difference = 604800
Month difference = 0
Days difference = 7
Year difference = 0

May help.

[lkagan]

Remember a caveat to using strtotime(), it is based on the UNIX epoch, 1/1/1970. Passing any dates before that as a parameter will give you a negative number of seconds which still works for calculations. Just don't try to pass the value back to date() or you'll always get 12/31/1969.