For years I've made sure to take a ride on my birthday. To me, like New Year's Day, your birthday signifies the start of a new year (although some poor souls seem to look at it as the end of a year). So, twice a calendar year, I start off a new year (calendar year, and Jon year) with a bike ride.
When I first started doing the b-day rides, I just made sure that I got a ride in on that day. I didn't really care how many miles I covered, so long as I rode on that particular day. On my 32nd birthday, for instance, I only rode 25 miles. But, that was 25 miles of a 100 mile, five-day/four-night biking and camping trip around the White Rim Trail, outside of Moab.
I was 35 when it occurred to me to make the mileage match my age. I figured that I had finally gotten old enough that matching my age would produce a significant ride distance. I have done at least my age for every birthday ride since then.
Now, however, I no longer care if the ride occurs exactly on my birthday. I work outside of the bike industry, and getting the day off just to go on a ride can be difficult. So, my 50th birthday ride will occur sometime this weekend. I rode today, but just about 20 miles to work and back (a detour has made my commute a few miles longer, for the past couple of weeks).
I hope to still do the birthday ride for another 50 years. I have to admit, though, that I might have to go metric at some point...