Representing ambiguity in datetime?

[Terry Hancock]

What do you do when a date or time is
incompletely specified?  ISTM, that as it is, there is no
formal way to store this --- you have to guess, and there's
no way to indicate that the guess is different from solid
information.  As a result, I have sometimes had to abandon
datetime, even though it seemed like the logical choice for
representing data.

E.g. I might have information like "this paper was published
in May 1997".  There's no way to write that with datetime,
is there?  Even if I just use the "date" object instead of 
datetime, I still have to actually specify something like 
May 1, 1997 --- fabricating data, which is frequently
undesireable (later on, I might find information saying that
it was actually published May 23, 1997 and I might want
to update the earlier one, or simply evaluate them as 
"equal" since they are, to within the precision given --- 
for example, I might be trying to decide that two database
entries are really duplicate references to the same paper).

I know that this is somewhat theoretically stated, but I 
have run into to concrete problems along the lines of
the above.

I'd say this is analogous to how you might use "None"
rather than "0" to represent an integer if you don't know
it's value (rather than knowing that it is zero).  ISTM, you
ought to be able to specify a date as, e.g.:

d = datetime.date(2005, 5, None)

I realize there might be some complexity with deciding
how to handle datestamp math, but as this situation
occurs frequently in real life, it seems like it shouldn't
be avoided.

How do other people deal with this kind of problem?

Cheers,
Terry

--
Terry Hancock ( hancock at anansispaceworks.com )
Anansi Spaceworks  http://www.anansispaceworks.com