I have found a simply way to hold both “hard landscape” and time-flexible tasks in one calendar. All You need is to mark “hard landscape” with speical color (I prefer orange, but You feel free to use any bright color - yellow will be a good choice). You can use Evolution, SunBird or MozillaCalendar and make some new calendar file of orange color, or You can use KOrganizer and reserve “Meetings” category for “hard landscape” items (don’t forget to assign orange color to this category). I don’t know is Outlook allow to assign specified colors to different categories (I hate Outlook at all).