Year+Week -&gt; Dates for a week

Year+Week -> Dates for a week

Anon

Given a year, and a week within the year:
eg. $year = 2001; $week = 8;

Is there an algorithm for finding all dates within the week ?

$year = 2001; $week = 8;

dates[0] = 19.02.2000;
dates[1] = 20.02.2000;
dates[2] = 21.02.2000;
..

I have tought about counting days from 01.01 and counting the weeks until the given week is reached, then finding the dates. but it seems like a very clumsy way to do it.

[deleted]

just a brainstorm:
can't you get the timestamp for 01-01-2000 or so, then add (assuming the 1st week is has number 1)
($number_of_weeks-1)(7246060) seconds to it, and convert that timestamp to a date?
then you loop 6 times adding 246060 to the timestamp to get the other days.

rolfnilsen

OK, this might work out.

The first week might have number 0 (01-01-2000 might be in week 52/53 the previous year thus 01-01-2000 might be in week 0 or 1).

But the method you propose for calculating seconds elapsed since 01-01-2000 until the start of the week is just what I wanted!

Thank you very much :-)

[deleted]

it gets worse: look at the annotations for the date() function in the php manual

-- quote --

robert.jackson@utoronto.ca
14-Aug-2000 11:02
I had to make a MySQL query for a given week (i.e. SELECT...WHERE date>='$last_sunday' AND date<='$next_saturday').

The php code I came up with is illustrated by:

$yr="2000";
$mnth="03";
$dy="02";
echo "base date: ".$yr."-".$mnth."-".$dy." ";
echo "last sunday: ".date("Y-m-d", mktime(0,0,0,$mnth,$dy-date("w",mktime(0,0,0,$mnth,$dy,$yr)),$yr))." ";
echo "next saturday: ".date("Y-m-d", mktime(0,0,0,$mnth,$dy+6-date("w",mktime(0,0,0,$mnth,$dy,$yr)),$yr))." ";

This seems to work within a month, across months (including leap years), and across years.

-- end quote --

rolfnilsen

I fail to see the implication with regards to my problem.

It would be very nice if you could explain why this makes my problem worse, as I'm happily coding this function now.

[deleted]

If I was "breaking my head" while witing a routine to do some calculations, I'd be pretty annoyed to find that someone else has already written such a routine. :-)

rolfnilsen

I see your point, but Robert Jackson already had a starting date. My problem was finding a date within the specified week..

Here are some code working snippets that solves my problem.

Thanks to you Vincent who pointed me in the right direction, Robert Jackson and Allan Kent for writing the code I have ripped and adapted.

<?
function dateAdd ($interval, $number, $date) {

/* The DateAdd function, according the VBScript documentation I have, "Returns a date to which a specified time interval has been added."

      The syntax is DateAdd(interval,number,date)

      The interval is a string expression that defines the interval you want to add. For example minutes or days,
      the number is the number of that interval that you wish to add, and the date is the date.

      Interval can be one of:

      yyyy     year
      q Quarter
      m Month
      y Day of year
      d Day
      w Weekday
      ww       Week of year
      h Hour
      n Minute
      s Second

$date_time_array = getdate($date);

$hours = $date_time_array["hours"];
$minutes = $date_time_array["minutes"];
$seconds = $date_time_array["seconds"];
$month = $date_time_array["mon"];
$day = $date_time_array["mday"];
$year = $date_time_array["year"];

switch ($interval) {

case "yyyy":
    $year +=$number;
    break;
case "q":
    $year +=($number*3);
    break;
case "m":
    $month +=$number;
    break;
case "y":
case "d":
case "w":
     $day+=$number;
    break;
case "ww":
     $day+=($number*7);
    break;
case "h":
     $hours+=$number;
    break;
case "n":
     $minutes+=$number;
    break;
case "s":
     $seconds+=$number;
    break;

}
$timestamp = mktime($hours ,$minutes, $seconds,$month ,$day, $year);
return $timestamp;
}
?>

<head>
<title></title>
</head>
<body>
<?

$year = 2004;
$week = 46;
$dweek = $week - 1;
echo "a day in week $week, year $year is : ".date("D d M Y",dateAdd("ww",$dweek, mktime (0, 0, 0, 1,1, $year) ))." ";

$month = date("m",dateAdd("ww",$dweek, mktime (0, 0, 0, 1,1, $year) ));
$day = date("d",dateAdd("ww",$dweek, mktime (0, 0, 0, 1,1, $year) ));

echo "base date: ".$year."-".$month."-".$day." ";
echo "last monday: ".date("Y-m-d", mktime(0,0,0,$month,$day+1-date("w",mktime(0,0,0,$month,$day,$year)),$year))." ";
echo "next sunday: ".date("Y-m-d", mktime(0,0,0,$month,$day+7-date("w",mktime(0,0,0,$month,$day,$year)),$year))." ";

?>
</body>