Step the current date forward step
days at a time (or backward, if step is negative) until we reach
limit (inclusive), yielding the resultant date at each step.
# File lib/date.rb, line 1338
def step(limit, step=1) # :yield: date
??
??
da = self
op = %w(- <= >=)[step <=> 0]
while da.__send__(op, limit)
yield da
da += step
end
self
end