In the process of looking at this I discovered (remember – I never use advanced search) that you cannot search using two (or more) of the date fields. For example, I searched for people with a birth in exactly 1922 and a death in exactly 1941. I know I have at least 1, but I got no result. I will investigate if that is possible as it would slightly help this topic, as you could search perhaps for births BEFORE 1939 and deaths after 1991 to answer Paul’s original issue.
I have been able to fix this. In the next release you will be able to search for multiple tags/places/dates. Attached is an example. I searched for individuals with my surname, born after 1900 in Surrey and died before 1991 in Kent.
Hopefully at least a partial solution to the questions raised in this thread.
(I hope to get the next release out in a week, or two at most).