We relate laws of large numbers and central limit theorems for nonstat
ionary counting processes to corresponding limits for their inverse pr
ocesses. We apply these results to develop approximations for queues t
hat are unstable in a nonstationary manner. We obtain unstable nonstat
ionary analogs of the queueing relation L = lambdaW and associated cen
tral-limit-theorem versions. For modeling and to obtain the first limi
ts, we can construct nonstationary point processes as random time-tran
sformations of familiar point processes, such as renewal processes and
stationary point processes. We deduce the asymptotic behavior of the
nonstationary point process from the asymptotic behavior of the famili
ar point process and the time transformation.