Adding days to a timestamp

Question

Giving a starting date, I\'m adding four times seven days to get 5 different dates separated exactly a week each one.

//$date = \'28-10-2010\';
$timestamp = mkti         


        

Answer 1

I will never understand why people use this horrible mktime function.

In case you are on PHP5.3 yet, you might want to consider using

$period = new DatePeriod(
    new DateTime('28-10-2010'),
    DateInterval::createFromDateString('1 week'),
    4);

foreach ( $period as $dt ) {
  echo $dt->format( "l Y-m-d H:i:s\n" );
}

Without PHP5.3 you can still use

for($i=0; $i<=4; $i++) {
    echo date('Y-m-d', strtotime("+$i weeks 28-10-2010")), PHP_EOL;
}

DateTime questions are pretty common on SO, so you might find interesting cases when searching.

Answer 2

It looks like you moved to daylight time savings or back from them.

POSIX time (timestamp) is always UTC while local time is UTC+X were X may change from date to date according to time savings.

Answer 3

It really seems to be time zone/DST related.

Adding

date_default_timezone_set('UTC');

as the first line solves the issue (as you no longer use any DST settings).

Answer 4

I have had a great deal of success with this methodology for adding days, though i have not tested with your format:

$date = The value of the database from your query
$daysahead = The number of days ahead you want to calculate
$final_date = date(“m/d/Y”, strtotime($date) + (86400 * $daysahead));

echo $final_date;

Answer 5

Never use math like 60*60*24*7 to add/subtract days (because of daylight time saving), use strtotime or mktime instead:

$timestamp = strtotime('+7 days', $timestamp);

// Or something like this (it's OK to have day parameter <= 0 or > 31)
$timestamp = mktime(0, 0, 0, $month, $day + 7, $year);

Your example will be more obvious if you'll output time as well:

$timestamp = mktime(0, 0, 0, 10, 28, 2010);
echo date('Y-m-d H:i:s', $timestamp) . "\n";

$timestamp += 60*60*24*7;
echo date('Y-m-d H:i:s', $timestamp) . "\n";

Output:

2010-10-28 00:00:00
2010-11-03 23:00:00

Here you have 2010-11-03 23:00:00 instead of 2010-11-04 00:00:00 because one of the days (31 Oct) is 25 hours long instead of 24.

Answer 6

In case someone needs this, just like me referencing the site: Today, current time, Y-m-d H:i:s, plus +7 Days. OR you could add +3 Months, etc.

$timestamp=strtotime("+7 Days");
$nowtime =  date('Y-m-d H:i:s', $timestamp);