It is one of those things left over from yesteryear. Tradition, I suppose.

Thanks for your answer. I will try it and thanks for making me aware of
some of the odd results I may obtain.

"Mike H" wrote:

I've never understood the value of using months in calculating age, is
someone born on 1 feb the same age as someone born 1 jan at the end of those
months? I think not. However, try this