1st Year Geo. Question

[GROSS CORY WALTER <GROS4891@ADC.MTROYAL.AB.CA>]

    Hello again,
    
        My 1st year Historical Geology professor gave my class this 
one question that we are supposed to find the answer for in our 
textbook. However, I can't find it anywhere and I was wondering if 
someone out there can help me. The question goes something like this:

        How have geologists determined that the number of days in the 
year has shortened over time?

        I also need the answer by Monday.  Thanx in advance...
        
Cory Gross
artist,writer,philosopher,scientist
gros4891@adc.mtroyal.ab.ca

                "Yes! What a goofy work is man!" -The Tick