You might consider doing something creative with the date field to make this work for your use case. For instance, instead of day/month/year you might decide that you were using that field for month/age/year that would give you 12 ages that are upto 9999 years long. Or you could do age/month/year which would give you a large number of ages to work with. Of course, this would mean that you would either have to rework your history somewhat to have ages that span less than 10000 years, or find some convenient spot to split long ages in half.
Just a thought.