Many many days ago I discovered that you can count your age not in years, but days.  I think I picked it up from reading stories or seeing TV shows about Indians, who liked to talk about time in “moons.”  It was a natural progression to continue that to days.  A day seems a more natural way to measure a life.  The day is the natural cycle of our lives.  The cycle of light and dark, wakefulness and sleep, has as much significance and more immediacy than the cycle of the seasons.  Each day is a complete unit in itself.  At the end of each day I can look back and take stock.  I can also look ahead a day with some degree of confidence it will be as I expect, unlike the years, which have been as unpredictable as a roulette wheel.  (And as exciting.)  I can hold a day's experience in mind quite easily. Trying to go back and take stock of a whole year is much harder, much less of many years.  Memory fades, not matter how hard you try and hold on to it. 
As you grow older the years accelerate as each year becomes a smaller percentage of your lifespan, so in truth, the years really do go by faster as you get older.  Doesn’t seem fair, does it?  But a day is a day is a day.
I also find it far more interesting to think that I have lived through nearly twenty thousand days this life, rather than 50 years. And it reframes the future.  I have -- probably -- thousands of days still to come.  Thousands of new days to do all the things I still have in mind to do.  So I’ve always just kind of liked the idea and have always known about where I was, day-wise, in my life.   So when I found this days-of-age calculator I had to put it on here, just for fun.  And to remind me to live today, not to wait until it’s “convenient”.