I will discuss a unified framework for studying late time cosmic acceleration. I will show that by using the methods of effective field theory, many of the existing models of dark energy can be subsumed in a single framework, rather than many compartmentalized theories. This approach has the advantage that existing observational constraints (which I will discuss) can be combined with theoretical consistency conditions such as locality and unitarity. By combining both types of constraints we will see that it is quite challenging to build realistic models to account for the current period of accelerated expansion.