Why doesn't timer's time_step work?

I set a float property for the time_step (bpy.context.scene.time_step), and initialized a timer using this code:

def execute(self, context):
wm = context.window_manager

When I print the time deltas between ticks (now - time.time()), they are ~0.0001. How can I change the time_step correctly? I even tried to set it with a constant, without any luck.