In Python, I do this to format date and time in a certain fashion.

  q = time.strftime('%Y-%m-%d', time.localtime())
  r = time.strftime('%H:%M:%S', time.localtime())

I am formatting by YYYY-MM-DD and HH:MM:SS (I keep dashes between the 
YYYY MM DD and colons between HH MM SS.

How is this done in Ruby?