The pulsed electromagnetic (EM) plane-wave scattering by a thin, high-contrast metasurface with time-varying magneto-dielectric properties is analyzed analytically with the aid of the time-domain (TD) EM reciprocity theorem of the time-convolution type. It is shown that the (1+1)-spacetime scattering problem can be reduced to a system of two uncoupled differential equations that are amenable to analytical solution. The resulting fields induced in the thin layer are subsequently used to express the desired scattered fields. The pertaining zero-reflection condition is discussed. Illustrative numerical examples are presented and validated numerically.