Re: Digikam as archive of historical photos

If your main concern is Date, you could use another program "in 
parallel" to Digikam.

I am thinking of Gramps, a FOSS genealogy program, which has a concept 
of fuzzy dates:

- exact date like 1776-07-04 (ISO 8601)
- shortened date 1776-07 (day unknown), 1776 (month and day unknown)
- approximate date "Before 1914', "After 1929", "About 1870" (the degree 
of uncertainty is a configurable setting, by default 50 for before and 
after, 5 for about)
- "interval date" as "Between 1914-08-03 and 1918-11-11"

There is also the notion of "duration" but it is irrelevant for photo 
archival.

Photos are recorded as Media objects with an associated Date. Only the 
path to the file is used. It can be absolute or relative to a "root".

Your photos can be managed in Digikam for comments and other purposes 
and date-evaluated in Gramps where you can query on date intervals. 
Unfortunately, there is no way to automatically link both programs. I 
suggest you either copy the "Gramps id" of the Media record into Digikam 
or use some Digikam-id into the Media record. The first alternative is 
probably the easiest one.