  This paper presents recent time-dependent measurements of neutral B meson
oscillations. Similar to the $K^0$--$\bar{K}^0$ system, there are two such
systems involving the b quark: $B_d^0$--$\bar{B}_d^0$ and
$B_s^0$--$\bar{B}_s^0$. Thus the physical states are respectively $K_{S}$ and
$K_{L}$, $(B_d)_S$ and $(B_d)_L$, and $(B_s)_S$ and $(B_s)_L$. The oscillation
between each pair of states can be used to determine their mass difference. The
present world average for the $(B_d)_S$--$(B_d)_L$ mass difference is $\Delta
m_d = 0.457\pm0.019 ps^{-1}$ (or $(3.01\pm0.13)\times 10^{-4}$ eV). Using
$f_{B_s}$ = 12\% (the fraction of $B_s$ produced in b events), the current
lower limit on the corresponding $\Delta m_s$ is 6.1 ps$^{-1}$ (or $4.0\times
10^{-3}$ eV).
