By highlighting I mean the day numbers of the months which (in general, as
you described in response to my original question) are emboldened if the day
contains an event which is shown as "Busy".

However the 2/10 month rule for emboldening does not appear to apply in the
case of my archive calender, which shows emboldened/highlighted dates over a
period of years (but it does not highlight consistently, in that some dates
which have events are not highlighted for some reason). Looking for
highlighted days is a good way of finding details of past events, providing
the highlighting process is reliable.

"Brian Tillman" wrote:

DavidMSPeace wrote:

However, I see that in my archive calendar file most of the "Busy"
items are highlighted, regardless of age - except that one or two are
not. It is possible that when the latter were first entered these
unhighlighted events were not marked as "Busy" but, in order to try
to pick them out more easily retrospectively, I have subsequently
changed them to "Busy". However, they remain stubbornly
unhighlighted. Are they a lost cause?

What are the highlighting rules for the archive file?

What highlighting do you mean? The Navigation Pane summarizes your delivery
location calendar only, as far as I can tell.
--
Brian Tillman [MVP-Outlook]