I've been doing some historical research, and I have a bunch of events
I'd like to be able to enter into some sort of chronological database.
My problem is that the dates I have vary widely in precision:

- exact date
- month and year
- year alone
- span from one month and year to another month and year
- span from one year to another year
- period like "late 80's" or "early 90's"

Ideally, I'd like to be able to enter the information in any of those
formats and then be able to search by year or month and get a list of
everything that fell within or included that time span. Is there any
freeware (or any free templates for something like Excel) that could do
that?