I took the realage test and it said that I am 12 years younger than my age. All I know for sure is that my 73 is not what my mother's 73 was! I keep physically active and have many interests that keep me busy and happy. I don't have the time or inclination to sit around and complain about getting old.
But good health is the main thing, age is no problem if you feel good.
As for my favorite birthday? I guess it will be this coming one, I plan to celebrate it by going on a birding trip to the Grand Teton National Park. Last year I celebrated by birding in the Big Bend park in Texas, and the year before by going caving in Mammoth Cave park. I figure that every birthday in the seventies should be special!