add and subtract day/week/month/year from unix time?

hi, topic says it all except that it must compensate for DST and such other things...

perfect answer would be 2 functions (add & sub) which take a unix timestamp and a value defining what unit (day, week, month, year)

i've tried alot of things myself, nothing seems to be perfect :)
clocKwizeAsked:
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Diablo84Commented:
Heres a basic function which covers both, il explain it in a follow up post

function altertime($stamp,$mode,$quantity,$unit) {
 $stamp = strtotime($mode.$quantity.$unit,$stamp);
 return $stamp;
}
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hernst42Commented:
Have you looked at the strtotime function ( http://de3.php.net/manual/en/function.strtotime.php )
e.g

echo strtotime("+1 day"), "\n";
actual-unix timestamp +1 day

echo strtotime("+1 week", $unixtimestamp), "\n";
$unixtimestamp +1 week
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Diablo84Commented:
the function is called altertime

the parameters are

$stamp - the timestamp
$mode - this is add "+" or sub "-"
$quantity - the number of days,weeks,months or years to add or subtract
$unit - "day" "week" "month" or "year"

example

function altertime($stamp,$mode,$quantity,$unit) {
 $stamp = strtotime($mode.$quantity.$unit,$stamp);
 return $stamp;
}

$time = time();
$newtime = altertime($time,"-",1,"day");
echo date("d m Y",$time);
echo "<br>";
echo date("d m Y",$newtime);
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Diablo84Commented:
heres a few other examples showing calling the function

$newtime = altertime($time,"-",10,"week"); //will return a timestamp 10 weeks before
$newtime = altertime($time,"+",1,"year"); //will return a timestamp 1 year after
$newtime = altertime($time,"+",2,"month"); //will return a timestamp 2 months after
$newtime = altertime($time,"-",2,"day"); //will return a timestamp 2 days before
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