Create alert/ reminders

Good afternoon,
I want to make a simple application where I have a form to enter the date and time that I want my application to tell me something.
Any suggestions?

Best Regards,
Silvio Neto

oh god, another one that likes cross posting
http://www.qtforum.org/article/37903/create-alerts.html

We obviously need to invest in a big hammer so we can whack these people when necessary.

Good morning,
I am developing an application to manage tasks of daily life. It needs to alert the software let I lacking a dialog, for example 30 minutes to perform that task.
How to solve this problem?
I need ideas and code if possible.
Greetings.