What software can I use to remind me of daily tasks?

[Mario Castelán Castro <marioxcc.MT@yandex.com>]

Hello.

I'm looking for a free (as in freedom) software that will remind me of 
daily tasks. That is it: one in which I can program reminders to be 
shown daily at a certain hour as a window to catch my attention or as a 
sound. I have searched in the web, but I have only found unmaintained 
software that doesn't do this.

Thanks in advance.