Two variational principles are discussed for time-dependent problems in reactor physics. The first is a stationary expression for the meter reading at a given time, the second a stationary expression for the integral of the meter reading up to a given time. Both the principles, unlike conventional Lagrangians extended to time-dependent nonconservative systems, have the advantage of requiring trial functions to be exact only at one end of the time interval of interest. Either may be generalized to account for nonlinearities. The second principle reduces to the first by making a suitable identification, while the first principle in turn reduces to a well-known and powerful variational principle for the steady state.