  We write down Crofton formulas--expressions that compute lengths of spacelike
curves in asymptotically AdS$_3$ geometries as integrals over kinematic
space--which apply when the curve and/or the background spacetime is
time-dependent. Relative to their static predecessor, the time-dependent
Crofton formulas display several new features, whose origin is the local null
rotation symmetry of the bulk geometry. In pure AdS$_3$ where null rotations
are global symmetries, the Crofton formulas simplify and become integrals over
the null planes, which intersect the bulk curve.
