Open sqllist.php from beginnerssite and save it as sqldateselect.php. Change the database name and the query so that it uses the task table and data you have just been using. Test it.
You can also use those date arithmetic methods to SELECT records from the database WHERE dates or times are equal to or less than/greater than a chosen time and date. In sqldateselect.php change the query to this:
SELECT tasktime, task FROM task WHERE tasktime<=DATE_ADD(NOW(), INTERVAL 1 DAY);
You should get fewer tasks (those with times within the next day) depending on how many you entered and whether you took a long break between the last page and this one! Add some more data if you need to.
The same principles apply to adding or subtracting months, years or times.