Scheduling reminders?

Is there some way to schedule reminders in LibreOffice? For example, if I want to remember to telephone someone next week on Monday at 1pm. Or if I need to remember to file my taxes next January 15th.

Currently I use a contact manager program (ACT!) but am trying to find an open source alternative to this increasingly complicated program that integrates a database with calendars and scheduled reminders but is all proprietary and, for me, becoming unstable.

Any advice would be deeply appreciated. Thank you!

Thunderbird is an open source SW with a calender; calender is an add on. Search the web for “mozilla thunderbird” for a download link.

Evolution is another, maybe better open source solution.
http://sourceforge.net/projects/evolution.mirror/