let say in your mysql database you are saving time on the datetime format
like this “2009-01-20 02:11:05″.

you need to pull it and add some days or time intervals and print it in a different format, thats easy do the following

1- In your query pulling the time, pull it this way:

UNIX_TIMESTAMP(time) AS time

this will covert it into unix timestamp, which will make it easier for you to manipulate it with php functions.

2- Add your time interval, let say we need to add 15 days.

$unix_timestamp_from_database = 1232410265;
$time_from_db = $unix_timestamp_from_database;
$new_time = $time_from_db + (15 * 86400);

86400seconds equals one day.
In unix timestamp we manipulate time by seconds.
so if you want to add an hour you add it like by (60 * 60)
which equals 3600 seconds.

3- Then you format it as you desire:

$new_time_format = date("d-M-Y", $new_time);
echo $new_time_format;

hope it will help you

To enable mod_rewrite in Ubuntu, you just need to write this command in terminal

sudo a2enmod rewrite