Global Virtual Time Approximation with Distributed Termination Detection Algorithms Technical Report RUU-CS-91-32, Department of Computer Science, University of Utrecht, The Netherlands, 1991 It is shown that distributed termination detection algorithms can be transformed into efficient algorithms to approximate the so-called Global Virtual Time (GVT) of a distributed monotonic computation. Typical instances of such computations are optimistic distributed simulations based on the time-warp principle. The transformation is exemplified for two termination detection algorithms, namely an algorithm by Dijkstra et al. and a new scheme based on the principle of "sticky flags". The general idea of the transformation is that many termination detection algorithms (viz., one for each possible GVT value) run in parallel. Each algorithm determines a specific lower bound on the current GVT value. In a straightforward way, the possibly infinite bundle of parallel termination detection algorithms can be combined into a single distributed algorithm which computes a tight lower bound on the GVT.