Snow Days, Holidays & Professional Days

One of the biggest challenges I find in my teaching is implementing my lessons around days off. Don't get me wrong I enjoy the days off. The difficulty comes when a class misses 2 classes in a row which sets that class behind the other classes in the same grade level. I find it easier to keep my grade level classes on the same lessons but missing days or shorten class periods due to delayed starts & early dismissal makes it impossible. Should I shorten & speed up the lesson for the class that has missed or slow down the lesson for the other classes? Often I choose to add a short enrichment lesson for the classes that are ahead.