Philsus:
There is also a new feature in S&T Keys v2.55.x (for S&T 2009 and 2010) and later called "calendar navigation" mode (see links in my signature). This is base on this same tip, but the main difference is that it will give you day/time display in S&T direction pane as you navigate automatically, keeping into account as you drive or add some unplanned stops to reajust the whole planning to take into account these events. So let's say that you planned first to leave the first day of your trip on march 16 at 10 am (you would see this on day 16 at 10h am in your planning if you are doing similar as the tip suggested), but you really started your trip on march 17 12h pm, your whole planning would be incorrect (and not display date/time correctly). Using calendar mode navigation in S&T Keys would adjust your complete planning day/time according your new date/time real departure automatically. The whole planning will also be recalculated each time you are stopping for lunch and it was not planned in your original planning.
So the tip Marvin is talking about can be used for planning before navigating, but once you start navigating, you may use calendar mode to keep S&T displaying date/time in direction pane correctly. The difference not using calendar mode to achieve date/time display is that you would have to tweak the direction pane stops manually yourself if you are driving does not follow exactly your original planning...
You should note that if you want to use both date/time display in planning mode and navigate with calendar mode later (with S&T Keys), you should probably remove the fake stop you added to display day/time in direction pane manually because S&T Keys will deal with it automatically and would add them as needed
See section 2.1.3 of S&T Keys 2009 online manual to get more details about calendar navigation mode