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checkdate> <Date/Time
Last updated: Fri, 28 Nov 2008

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Date/Time Functions

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checkdate> <Date/Time
Last updated: Fri, 28 Nov 2008
 
add a note add a note User Contributed Notes
Date/Time Functions
ryan
05-Aug-2008 04:59
Actually in regards to sagar's week functionality, there's a much better way. Well, to at least get the start_timestamp. I'm sure y'all can figure out the end_timestamp on your own. This is part of a script I wrote some time back and uses $_GET['year'] and $_GET['week'] if the user was moving around the calendar. Otherwise it loaded the current week.

Some might ask about January 4th, but according to the official ISO specification or something, January 4th is always in week 1, so it works out.

Oh... and it doesn't work with daylight savings time as well but since it starts on a Monday, for the most part, it won't affect really anything.

<?php
  // Get today
  $date = time();

  // Get times (minute, hour, day) in seconds
  $ms = 1 * 60;
  $hs = 1 * 60 * $ms;
  $ds = 1 * 24 * $hs;

  // Get first day in the week
  if ( is_numeric($_GET['year']) && is_numeric($_GET['week']) )
  {
    $first = strtotime('January 4 '.$_GET['year'].' + '.($_GET['week'] - 1).' weeks');
    $first = $first - $ds * ( date('w', $first) - 1 );
  }
  else
    $first = $date - ( $ds * ( date('w', $date) - 1 ) + $hs * date('H', $date) + $ms * date('i', $date) + date('s', $date) );
?>
Robb_Bean at gmx dot nospam dot net
19-Mar-2008 12:47
With PHP 5.1 and 5.2 the languages datetime support has changed. Although these functions should guess your local timezone settings, they may fail if using a default configuration in a "pre-5.1 way", which means setting no timezone for PHP. In the case PHP could not get a timezone it emits a E_STRICT warning. Note that this affects _all_ datetime functions and keep it in mind when porting software from previous versions to 5.1 or later! It may also confuse your error handling (this is the way I noticed that things have changed, since these changes are not documentated _here_).

References:

http://www.php.net/manual/de/migration51.datetime.php
http://www.php.net/manual/de/migration52.datetime.php
sagar
28-Feb-2008 05:53
<?php
####################################
# Provide week number and get start_timestamp and end_timestamp
#####################################

// this week number will come from the timeshare form
 $week = 51;

$times = get_start_and_end_date_from_week($week);
$start_time = $times['start_timestamp'];
$end_time = $times['end_timestamp'];

function get_start_and_end_date_from_week ($w)
{
    $y = date("Y", time());
    $o = 6; // week starts from sunday by default

    $days = ($w - 1) * 7 + $o;

    $firstdayofyear = getdate(mktime(0,0,0,1,1,$y));
    if ($firstdayofyear["wday"] == 0) $firstdayofyear["wday"] += 7;
    # in getdate, Sunday is 0 instead of 7
    $firstmonday = getdate(mktime(0,0,0,1,1-$firstdayofyear["wday"]+1,$y));
    $calcdate = getdate(mktime(0,0,0,$firstmonday["mon"], $firstmonday["mday"]+$days,$firstmonday["year"]));

    $sday = $calcdate["mday"];
    $smonth = $calcdate["mon"];
    $syear = $calcdate["year"];
   
       
    $timestamp['start_timestamp'] =  mktime(0, 0, 0, $smonth, $sday, $syear);
    $timestamp['end_timestamp'] =  $timestamp['start_timestamp'] + (60*60*24*7);

    return $timestamp;

}    # function datefromweek
?>
nate at example dot com
05-Feb-2008 01:56
Here's my version of date diff that handles leap years, DST, and deals with the diff in terms of "human calculations". For example, this code does not assume that a year = 365.25 days, or that a month = 30/31 days. The results are exactly what a human being would determine as a good result.

<?php

/**
 * this code assumes php >= 5.1.0. if using < 5.1, read
 * php.net/strtotime and change the condition for checking
 * for failure from strtotime()
 */

// $t1, $t2: unix times, or strtotime parseable
// $precision: max number of units to output
// $abbr: if true, use "hr" instead of "hour", etc.
function date_diff ($t1, $t2, $precision = 6, $abbr = false) {
    if (preg_match('/\D/', $t1) && ($t1 = strtotime($t1)) === false)
        return false;

    if (preg_match('/\D/', $t2) && ($t2 = strtotime($t2)) === false)
        return false;

    if ($t1 > $t2)
        list($t1, $t2) = array($t2, $t1);

    $diffs = array(
        'year' => 0, 'month' => 0, 'day' => 0,
        'hour' => 0, 'minute' => 0, 'second' => 0,
    );

    $abbrs = array(
        'year' => 'yr', 'month' => 'mth', 'day' => 'day',
        'hour' => 'hr', 'minute' => 'min', 'second' => 'sec'
    );

    foreach (array_keys($diffs) as $interval) {
        while ($t2 >= ($t3 = strtotime("+1 ${interval}", $t1))) {
            $t1 = $t3;
            ++$diffs[$interval];
        }
    }

    $stack = array();
    foreach ($diffs as $interval => $num)
        $stack[] = array($num, ($abbr ? $abbrs[$interval] : $interval) . ($num != 1 ? 's' : ''));

    $ret = array();
    while (count($ret) < $precision && ($item = array_shift($stack)) !== null) {
        if ($item[0] > 0)
            $ret[] = "{$item[0]} {$item[1]}";
    }

    return implode(', ', $ret);
}

$t1 = 'Feb 4, 2008 12:16:00';
$t2 = 'Jul 3, 2006 16:15:30';

echo date_diff($t1, $t2), "\n",
    date_diff($t1, $t2, 3), "\n",
    date_diff($t1, $t2, 2, true), "\n";

?>
stoicnluv at gmail dot com
06-Nov-2007 12:14
A better and accurate function to calculate the difference between 2 dates. Takes leap years and DST into consideration. Accepts string date or timestamp as arguments.

<?php
function date_diff($d1, $d2){
    $d1 = (is_string($d1) ? strtotime($d1) : $d1);
    $d2 = (is_string($d2) ? strtotime($d2) : $d2);

    $diff_secs = abs($d1 - $d2);
    $base_year = min(date("Y", $d1), date("Y", $d2));

    $diff = mktime(0, 0, $diff_secs, 1, 1, $base_year);
    return array(
        "years" => date("Y", $diff) - $base_year,
        "months_total" => (date("Y", $diff) - $base_year) * 12 + date("n", $diff) - 1,
        "months" => date("n", $diff) - 1,
        "days_total" => floor($diff_secs / (3600 * 24)),
        "days" => date("j", $diff) - 1,
        "hours_total" => floor($diff_secs / 3600),
        "hours" => date("G", $diff),
        "minutes_total" => floor($diff_secs / 60),
        "minutes" => (int) date("i", $diff),
        "seconds_total" => $diff_secs,
        "seconds" => (int) date("s", $diff)
    );
}

$a = date_diff("2006-11-01", "2007-11-01");

echo "<pre>";
print_r($a);
echo "</pre>";
?>

This example will output (if your timezone uses US DST):

Array
(
    [years] => 0
    [months_total] => 11
    [months] => 11
    [days_total] => 364
    [days] => 30
    [hours_total] => 8759
    [hours] => 23
    [minutes_total] => 525540
    [minutes] => 0
    [seconds_total] => 31532400
    [seconds] => 0
)

As you can see, the result is not exactly 1 year (less 1 hour) since Nov 1, 2006 is not DST while Nov 1, 2007 is DST.
venoel at rin dot ru
26-Oct-2007 12:33
May be useful for somebody. This function takes on daylight saving time

<?php
Function DateDiff($date1,$date2) {
  $timedifference=$date2-$date1;
  $corr=date("I",$date2)-date("I",$date1);
  $timedifference+=$corr;
  return $timedifference;
}
?>

Example:

<?php
$d1=mktime(2,0,0,10,28,2007);
$d2=mktime(4,0,0,10,28,2007);
$period=DateDiff($d1,$d2);
printf("<br>%s",date("I d.m.Y H:i",$d1));
printf("<br>%u hour",$period/3600);
printf("<br>%s",date("I d.m.Y H:i",$d2));
?>

Getting 2 hour instead 3.
koch.ro
17-Oct-2007 09:42
Not really elegant, but tells you, if your installed timezonedb is the most recent:

<?php
class TestDateTimeTimezonedbVersion extends PHPUnit_Framework_TestCase
{
    public function testTimezonedbIsMostRecent()
    {
        ini_set( 'date.timezone', 'Europe/Berlin' );
        ob_start();                                                                                                       
        phpinfo(INFO_MODULES);
        $info = ob_get_contents();                                                                                        
        ob_end_clean();
        $start = strpos( $info, 'Timezone Database Version' ) + 29;

        $this->assertTrue( FALSE !== $start, 'Seems there is no timezone DB installed' );

        $end   = strpos( $info, "\n", $start );
        $installedVersion = substr( $info, $start, $end - $start );

        exec( 'pecl remote-info timezonedb', &$output );
        $availableVersion = substr( $output[2], 12 );

        $this->assertEquals( $availableVersion, $installedVersion,
        'The installed timezonedb is not actual. Installed: '.$installedVersion
        .' available: '.$availableVersion
        );
    }
}
?>
herbert DOT fischer ATT gEE mail DOT com
11-Oct-2007 10:44
Updating internal's PHP timezone database (5.1.x and 5.2.x)

http://fischer.tecnologia.ws/en/node/1

[editor: Although this does work, it's often easier just to install the pecl timezonedb extension - they should be up-to-date with the latest possible information]
aquatakat at telus dot net
24-Sep-2007 10:25
I wrote a simple script to format a duration in seconds. Give the function some value in seconds and it will return an array.

<?php

function format_duration($seconds) {

    $periods = array(
        'centuries' => 3155692600,
        'decades' => 315569260,
        'years' => 31556926,
        'months' => 2629743,
        'weeks' => 604800,
        'days' => 86400,
        'hours' => 3600,
        'minutes' => 60,
        'seconds' => 1
    );

    $durations = array();

    foreach ($periods as $period => $seconds_in_period) {
        if ($seconds >= $seconds_in_period) {
            $durations[$period] = floor($seconds / $seconds_in_period);
            $seconds -= $durations[$period] * $seconds_in_period;
        }
    }
   
    return $durations;

}

echo format_duration(864);

/*
[minutes] => 14
[seconds] => 24
*/

echo format_duration(3600);

/*
[hours] => 1
*/

echo format_duration(11111111);

/*
[months] => 4
[days] => 6
[hours] => 20
[minutes] => 28
[seconds] => 59
*/

?>
Darren Edwards
06-Sep-2007 05:54
I was looking for a solution where I could return the number of days, hours, Minutes and seconds between two entries in a table.
DATE_DIFF is not running on my mysql server as my provider uses mysql version 4.0.25
Solution was to use to days and std time functions to calculate the difference in one call.
The fields stored in the table(report_table) are
time(00:00:00),
date(0000-00-00) and record(enum) which tells the app the type of log stored. EG start or end of a report.

SELECT
(TO_DAYS( `end`.`date` ) - TO_DAYS( `start`.`date` ))
-
( second( `end`.`time` ) + (minute( `end`.`time` )*60) + (hour( `end`.`time` )*3600)
<
 second( `start`.`time` ) + (minute( `start`.`time` )*60) + (hour( `start`.`time` )*3600))
AS `days` ,
SEC_TO_TIME(
(second( `end`.`time` ) + (minute( `end`.`time` )*60) + (hour( `end`.`time` )*3600) )
-
(second( `start`.`time` ) + (minute( `start`.`time` )*60) + (hour( `start`.`time` )*3600) )
 ) AS `hms`,
`start`.`time` as `start`,
`end`.`time`  as `end`

FROM `report_table` AS `start` , `report_table` AS `end`
AND `start`.`record` = 'Report Begin'
AND `end`.`record` = 'Report End'
LIMIT 1

If there is no end of report then it will not return a result, as you would expect.
Leopoldo A dot Oducado (poducado at comfsm dot fm)
16-Feb-2007 04:50
Here is my function to count the number days, weeks, months, and year. I tried it below 1970 and it works.

<?php
function datecal($date,$return_value)
{
$date = explode("/", $date);
$month_begin = $date[0];
$month_begin_date = $date[1];
$year1 = $date[2];
$month_end = date("n");
$month_end_date = date("j");
$year2 = date("Y");
$days_old = 0;
$years_old = 0;
$months_old = 0;
if($month_begin==12)
{
  $month = 1;
  $year = $year1+1;
}
else
{
  $month = $month_begin+1;
  $year = $year1;
}
$begin_plus_days = cal_days_in_month(CAL_GREGORIAN, $month_begin, $year1) - $month_begin_date;
$end_minus_days = cal_days_in_month(CAL_GREGORIAN, $month_end, $year2) - $month_end_date;
while ($year <= $year2)
{   
     if($year == $year2)
    {
      $days_old = $days_old + cal_days_in_month(CAL_GREGORIAN, $month, $year);    
      if($month < $month_end)
        {
         $months_old = $months_old + 1;   
         $month = $month + 1;
        }
          elseif ($month==$month_end and $month_end_date >= $month_begin_date)
            {
         $year = $year2+1;   
        }
      else
        {   
         $year = $year2+1;   
        }
    }
    else
    {
     $days_old = $days_old + cal_days_in_month(CAL_GREGORIAN, $month, $year);
         if ($month <= 11)
            {
         $month = $month + 1;
         $months_old = $months_old + 1;   
            }
         else
            {
         $month = 1;
         $year = $year + 1;
         $months_old = $months_old + 1;       
            }    
    }
}
$days_old = ($days_old + $begin_plus_days) - $end_minus_days;
if($return_value == "d")
  { return $days_old; }
elseif ($return_value == "w")
  { return intval($days_old/7); }
elseif ($return_value == "m")
  { return $months_old; }
elseif ($return_value == "y")
  { return intval($months_old/12); }
}

echo datecal("08/13/1975","m");
?>
bgold at matrix-consultants dot com
17-Jan-2007 02:08
When debugging code that stores date/time values in a database, you may find yourself wanting to know the date/time that corresponds to a given unix timestamp, or the timestamp for a given date & time.

The following script will do the conversion either way.  If you give it a numeric timestamp, it will display the corresponding date and time.  If you give it a date and time (in almost any standard format), it will display the timestamp.

All conversions are done for your locale/time zone.

<?php
        while (true)
        {
                // Read a line from standard in.
                echo "enter time to convert: ";
                $inline = fgets(STDIN);
                $inline = trim($inline);
                if ($inline == "" || $inline == ".")
                        break;

                // See if the line is a date.
                $pos = strpos($inline, "/");
                if ($pos === false) {
                        // not a date, should be an integer.
                        $date = date("m/d/Y G:i:s", $inline);
                        echo "int2date: $inline -> $date\n";
                } else {
                        $itime = strtotime($inline);
                        echo "date2int: $inline -> $itime\n";
                }
        }
?>
mikeb at tracersinfo dot com
06-Nov-2006 08:27
Another month late on this, but I would amend alex's post to recommend using gmdate() any time you're trying to represent a "delta time", or your local timezone is likely to interfere.

For example, a five minute difference (300 seconds) would appear as follows in New York:

echo date('z:H:i:s', 300);
// 364:19:05:00

echo gmdate('z:H:i:s', 300);
// 0:00:05:00

Thanks for the 'z', though, Alex.  Up until now, I've always been dividing that out -- hadn't found it in the format list.  :-)
alex dot stevenson at t8design dot com
12-Sep-2006 06:50
A few months late on this, but I just saw cepercival at thatMailThatsHot dot com 's post, and think that it may be a bit easier to just use this as opposed to writing it by hand:

date("z:H:i:s", $endTimestamp - $startTimestamp);

Since the timestamps store seconds from the unix epoch, and the unix epoch occured at the very beginning of a year, you can get away with this.

It gets a little trickier to place the years, but it should work fine if you subtract out the number of years date("Y", 0) returns.  This would naturally require two seperate calls to the date function- one to find the year, and one to find the rest of the information.
cepercival at thatMailThatsHot dot com
11-Jul-2006 02:31
Hopefully this may be useful to someone out there!
I wanted a simple function to give me a duration for phone calls using a start timestamp and end timestamp. After finding an understandable example here http://www.brenlei.com/articles/php/dates/dates4.php i cobbled this together:

<?php
function callDuration($dateTimeBegin,$dateTimeEnd) {
      
      $dif=$dateTimeEnd - $dateTimeBegin;

      $hours = floor($dif / 3600);
      $temp_remainder = $dif - ($hours * 3600);
       
      $minutes = floor($temp_remainder / 60);
      $temp_remainder = $temp_remainder - ($minutes * 60);
       
      $seconds = $temp_remainder;
         
      // leading zero's - not bothered about hours
      $min_lead=':';
     if($minutes <=9)
        $min_lead .= '0';
      $sec_lead=':';
     if($seconds <=9)
        $sec_lead .= '0';
       
  // difference/duration returned as Hours:Mins:Secs e.g. 01:29:32

  return $hours.$min_lead.$minutes.$sec_lead.$seconds;
       
       }
?>

obviously it can be easily extended to include days, weeks etc.
Stupidly simple I know but that's how i like it.
andreencinas at yahoo dot com dot br
28-Sep-2005 02:08
<?php
       //function like dateDiff Microsoft
       //not error in year Bissesto

       function dateDiff($interval,$dateTimeBegin,$dateTimeEnd) {
         //Parse about any English textual datetime
         //$dateTimeBegin, $dateTimeEnd

         $dateTimeBegin=strtotime($dateTimeBegin);
         if($dateTimeBegin === -1) {
           return("..begin date Invalid");
         }

         $dateTimeEnd=strtotime($dateTimeEnd);
         if($dateTimeEnd === -1) {
           return("..end date Invalid");
         }

         $dif=$dateTimeEnd - $dateTimeBegin;

         switch($interval) {
           case "s"://seconds
               return($dif);

           case "n"://minutes
               return(floor($dif/60)); //60s=1m

           case "h"://hours
               return(floor($dif/3600)); //3600s=1h

           case "d"://days
               return(floor($dif/86400)); //86400s=1d

           case "ww"://Week
               return(floor($dif/604800)); //604800s=1week=1semana

           case "m": //similar result "m" dateDiff Microsoft
               $monthBegin=(date("Y",$dateTimeBegin)*12)+
                 date("n",$dateTimeBegin);
               $monthEnd=(date("Y",$dateTimeEnd)*12)+
                 date("n",$dateTimeEnd);
               $monthDiff=$monthEnd-$monthBegin;
               return($monthDiff);

           case "yyyy": //similar result "yyyy" dateDiff Microsoft
               return(date("Y",$dateTimeEnd) - date("Y",$dateTimeBegin));

           default:
               return(floor($dif/86400)); //86400s=1d
         }

       }
?>
glashio at xs4all dot nl
27-Sep-2005 09:46
Calculate Sum BusinessDays (Mon till Fri) between two date's :

<?php
function businessdays($begin, $end) {
    $rbegin = is_string($begin) ? strtotime(strval($begin)) : $begin;
    $rend = is_string($end) ? strtotime(strval($end)) : $end;
    if ($rbegin < 0 || $rend < 0)
        return 0;

    $begin = workday($rbegin, TRUE);
    $end = workday($rend, FALSE);

    if ($end < $begin) {
        $end = $begin;
        $begin = $end;
    }

    $difftime = $end - $begin;
    $diffdays = floor($difftime / (24 * 60 * 60)) + 1;

    if ($diffdays < 7) {
        $abegin = getdate($rbegin);
        $aend = getdate($rend);
        if ($diffdays == 1 && ($astart['wday'] == 0 || $astart['wday'] == 6) && ($aend['wday'] == 0 || $aend['wday'] == 6))
            return 0;
        $abegin = getdate($begin);
        $aend = getdate($end);
        $weekends = ($aend['wday'] < $abegin['wday']) ? 1 : 0;
    } else
        $weekends = floor($diffdays / 7);
    return $diffdays - ($weekends * 2);
}

function workday($date, $begindate = TRUE) {
    $adate = getdate($date);
    $day = 24 * 60 * 60;
    if ($adate['wday'] == 0) // Sunday
        $date += $begindate ? $day : -($day * 2);
    elseif ($adate['wday'] == 6) // Saterday
        $date += $begindate ? $day * 2 : -$day;
    return $date;
}
?>
daniel at globalnetstudios dot com
08-Jun-2005 08:49
This dateDiff() function can take in just about any timestamp, including UNIX timestamps and anything that is accepted by strtotime(). It returns an array with the ability to split the result a couple different ways. I built this function to suffice any datediff needs I had. Hope it helps others too.

<?php
  /********* dateDiff() function **********
   * returns Array of Int values for difference between two dates
   * $date1 > $date2 --> positive integers are returned
   * $date1 < $date2 --> negative integers are returned
   *
   * $split recognizes the following:
   *   'yw' = splits up years, weeks and days (default)
   *   'y'  = splits up years and days
   *   'w'  = splits up weeks and days
   *   'd'  = total days
   *
   * examples:
   *   $dif1 = dateDiff() or dateDiff('yw')
   *   $dif2 = dateDiff('y')
   *   $dif3 = dateDiff('w')
   *   $dif4 = dateDiff('d')
   *
   * assuming dateDiff returned 853 days, the above
   * examples would have a print_r output of:
   *   $dif1 == Array( [y] => 2 [w] => 17 [d] => 4 )
   *   $dif2 == Array( [y] => 2 [d] => 123 )
   *   $dif3 == Array( [w] => 121 [d] => 6 )
   *   $dif4 == Array( [d] => 847 )
   *
   * note: [h] (hours), [m] (minutes), [s] (seconds) are always returned as elements of the Array
   */
  function dateDiff($dt1, $dt2, $split='yw') {
    $date1 = (strtotime($dt1) != -1) ? strtotime($dt1) : $dt1;
    $date2 = (strtotime($dt2) != -1) ? strtotime($dt2) : $dt2;
    $dtDiff = $date1 - $date2;
    $totalDays = intval($dtDiff/(24*60*60));
    $totalSecs = $dtDiff-($totalDays*24*60*60);
    $dif['h'] = $h = intval($totalSecs/(60*60));
    $dif['m'] = $m = intval(($totalSecs-($h*60*60))/60);
    $dif['s'] = $totalSecs-($h*60*60)-($m*60);
    // set up array as necessary
    switch($split) {
    case 'yw': # split years-weeks-days
      $dif['y'] = $y = intval($totalDays/365);
      $dif['w'] = $w = intval(($totalDays-($y*365))/7);
      $dif['d'] = $totalDays-($y*365)-($w*7);
      break;
    case 'y': # split years-days
      $dif['y'] = $y = intval($totalDays/365);
      $dif['d'] = $totalDays-($y*365);
      break;
    case 'w': # split weeks-days
      $dif['w'] = $w = intval($totalDays/7);
      $dif['d'] = $totalDays-($w*7);
      break;
    case 'd': # don't split -- total days
      $dif['d'] = $totalDays;
      break;
    default:
      die("Error in dateDiff(). Unrecognized \$split parameter. Valid values are 'yw', 'y', 'w', 'd'. Default is 'yw'.");
    }
    return $dif;
  }
?>
mail at completeideas dot com
06-Jun-2005 10:55
For those who are using pre MYSQL 4.1.1, you can use:

TO_DAYS([Date Value 1])-TO_DAYS([Date Value 2])

For the same result as:

DATEDIFF([Date Value 1],[Date Value 2])
mincklerstraat at softhome dot net
11-Oct-2004 10:43
Before you get too advanced using date functions, be sure also to see the calendar functions at http://www.php.net/manual/en/ref.calendar.php .
nickaubert at america's biggest isp dot com
12-Apr-2004 10:13
I ran into an issue using a function that loops through an array of dates where the keys to the array are the Unix timestamp for midnight for each date.  The loop starts at the first timestamp, then incremented by adding 86400 seconds (ie. 60 x 60 x 24).  However, Daylight Saving Time threw off the accuracy of this loop, since certain days have a duration other than 86400 seconds.  I worked around it by adding a couple of lines to force the timestamp to midnight at each interval.

<?php
  $ONE_DAY = 90000;   // can't use 86400 because some days have one hour more or less
  for ( $each_timestamp = $start_time ; $each_timestamp <= $end_time ; $each_timestamp +=  $ONE_DAY) {

    /*  force midnight to compensate for daylight saving time  */
    $this_timestamp_array = getdate( $each_timestamp );
    $each_timestamp = mktime ( 0 , 0 , 0 , $this_timestamp_array[mon] , $this_timestamp_array[mday] , $this_timestamp_array[year] );

     // do some stuff...
  }
?>
php at sarge dot ch
28-Jan-2004 01:58
Additional thisone here (didn't test it yet but should work :D):

<?php
/**
 * Calculates the Difference between two timestamps
 *
 * @param integer $start_timestamp
 * @param integer $end_timestamp
 * @param integer $unit (default 0)
 * @return string
 * @access public
 */
function dateDifference($start_timestamp,$end_timestamp,$unit= 0){
  $days_seconds_star= (23 * 56 * 60) + 4.091; // Star Day
  $days_seconds_sun= 24 * 60 * 60; // Sun Day
  $difference_seconds= $end_timestamp - $start_timestamp;
  switch($unit){
    case 3: // Days
      $difference_days= round(($difference_seconds / $days_seconds_sun),2);
      return 'approx. '.$difference_hours.' Days';
    case 2: // Hours
      $difference_hours= round(($difference_seconds / 3600),2);
      return 'approx. '.$difference_hours.' Hours';
    break;
    case 1: // Minutes
      $difference_minutes= round(($difference_seconds / 60),2);
      return 'approx. '.$difference_minutes.' Minutes';
    break;
    default: // Seconds
      if($difference_seconds > 1){
        return $difference_seconds.' Seconds';
      }
      else{
        return $difference_seconds.' Second';
      }
  }
}
?>
php at elmegil dot net
20-Dec-2003 07:40
A much easier way to do days diff is to use Julian Days from the Calendar functions:

$start = gregoriantojd($smon, $sday, $syear);
$end = gregoriantojd($emon, $eday, $eyear);
$daysdiff = $end - $start;

You can see the obvious ways to wrap a function around that.
garyc at earthling dot net
19-Mar-2003 05:08
I needed to calculate the week number from a given date and vice versa, where the week starts with a Monday and the first week of a year may begin the year before, if the year begins in the middle of the week (Tue-Sun). This is the way weekly magazines calculate their issue numbers.

Here are two functions that do exactly that:

Hope somebody finds this useful.

Gary

<?php
/*  w e e k n u m b e r  -------------------------------------- //
weeknumber returns a week number from a given date (>1970, <2030)
Wed, 2003-01-01 is in week 1
Mon, 2003-01-06 is in week 2
Wed, 2003-12-31 is in week 53, next years first week
Be careful, there are years with 53 weeks.
// ------------------------------------------------------------ */

function weeknumber ($y, $m, $d) {
    $wn = strftime("%W",mktime(0,0,0,$m,$d,$y));
    $wn += 0; # wn might be a string value
    $firstdayofyear = getdate(mktime(0,0,0,1,1,$y));
    if ($firstdayofyear["wday"] != 1)    # if 1/1 is not a Monday, add 1
        $wn += 1;
    return ($wn);
}    # function weeknumber

/*  d a t e f r o m w e e k  ---------------------------------- //
From a weeknumber, calculates the corresponding date
Input: Year, weeknumber and day offset
Output: Exact date in an associative (named) array
2003, 12, 0: 2003-03-17 (a Monday)
1995,  53, 2: 1995-12-xx
...
// ------------------------------------------------------------ */

function datefromweek ($y, $w, $o) {

    $days = ($w - 1) * 7 + $o;

    $firstdayofyear = getdate(mktime(0,0,0,1,1,$y));
    if ($firstdayofyear["wday"] == 0) $firstdayofyear["wday"] += 7;
# in getdate, Sunday is 0 instead of 7
    $firstmonday = getdate(mktime(0,0,0,1,1-$firstdayofyear["wday"]+1,$y));
    $calcdate = getdate(mktime(0,0,0,$firstmonday["mon"], $firstmonday["mday"]+$days,$firstmonday["year"]));

    $date["year"] = $calcdate["year"];
    $date["month"] = $calcdate["mon"];
    $date["day"] = $calcdate["mday"];

    return ($date);

}    # function datefromweek
?>
brighn (a) yahoo (.) com
03-Jan-2003 06:46
I needed a function that determined the last Sunday of the month. Since it's made for the website's "next meeting" announcement, it goes based on the system clock; also, if today is between Sunday and the end of the month, it figures out the last Sunday of *next* month. lastsunday() takes no arguments and returns the date as a string in the form "January 26, 2003". I could probably have streamlined this quite a bit, but at least it's transparent code. =)

<?php
  /* The two functions calculate when the next meeting will
     be, based on the assumption that the meeting will be on
     the last Sunday of the month. */ 

  function getlast($mon, $year) {
    $daysinmonth = array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
    $days = $daysinmonth[$mon-1];
    if ($mon == 2 && ($year % 4) == 0 && (($