Re: RE: Tiki.Spreadsheet
Using Trackers is another way of handling your data. Read the docs.
This might be of some interest for you:
https://doc.tiki.org/PluginTrackerCalendar
(you also have a profile in the the "Profiles Wizard" in Tiki12 to help you set up one for your site: "Tracker_as_Calendar_10")
Did I already say "Read the docs"? ;-)