Finding date of next day

Anon

I've tried and tried before posting a request for help, but to no avail. I've even tried searching for help on it, but also no dice.

I'm looking for a formula to find the date of a specified day after a certain date. Example, the person enters a date of 8/13/02 and I need to find the date of the day following that user specifies. So if they specify Friday, I need to find the date of the next Friday which would be 8/16/03.

Anon

Find the position in the week of the date the user entered (date("w", $USER_TIMESTAMP))
Then, calculate the numeric distance between the day you want and the one entendes by user.
Suppose the user entered 1 (Monday) and you want 5 (Friday), 5 - 1 = 4 (wanted day - user day = y)

But suppose the user entered 6 (Saturday) and you want 5... 5 - 6 = -1 ! No problem ! 5 + 7 = 12, 12 - 6 = 6 (wanted day + number of days in week = x, x - user dat = y)

Now, what do we do with y...

First, we'll use mktime :
$user_timestamp = mktime(0, 0, 0, $user_month, $user_day, $user_year);

Second, since there are 86 400 seconds in one day, we will multiply it by the number of days between the two days (y)...

$wanted_timestamp = $user_timestamp + (86400 * $y);

$y is what we found above... 12 - 6 = 6, ...

That will give you a new timestamp as wanted !

Let's put that together...

<?
$user_timestamp = mktime(0, 0, 0, $user_month, $user_day, $user_year);
$user_weekday = date("w", $user_timestamp);
$wanted_weekday = 5;
$diff = $wanted_weekday - $user_weekday;
if($diff == 0) {
$diff = 7;
} elseif($diff < 0) {
$diff = $wanted_weekday + 7 - $user_weekday;
}
$new_timestamp = $user_timestamp + (86400 * $diff);
$new_month = date("n", $new_timestamp);
$new_day = date("j", $new_timestamp);
$new_year = date("Y", $new_timestamp);
echo "New date is $new_day/$new_month/$new_year";
?>

$user_month, $user_day and $user_year are the infos entered by the user... from a form for example...

I hope it will help you ! It works perfectly on my computer !

Anon

Thanx so much. I'm still not too familiar with the date functions and such. It's working so far.

Anon

Yikes.

If you want to figure out how far the next day is away from a certain day, use php to do it.

First you'll have to convert your form input into seconds by using the following:

$date = mktime(0,0,0,$month,$day,$year);

Now do some math:

60 seconds per minute X 60 minutes per hour X 24 hours per day = 86400 seconds per day.

So, the NEXT day will be:

$next_day = $date + 86400;

Want a week from now? Multiply 86400 x 7. I think that is a lot easier to understand and implement then playing with mysql's date functions.

Have fun!