If there is Earth Hour, how about Bike Hour? Why not? From cycle-space.com from where the idea originated:
The world’s biggest, completely unorganised, mass cycling rally will happen wherever you are, on Tuesday March 20, between 6 and 7 pm. Why? Because you will be riding your bike.
Ride how you like, where you like, with whom you like, or ride alone. Just get on your bike and pedal the sucker. By doing so, you will be showing the world our staggering numbers, and unspoken yearning for safer, more edifying, cycling conditions.
Mark the date, folks for the first ever Bike Hour: July 20th, 6:00 – 7:00 pm. See you on the streets.