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Abstract: Strong tidal forces can dominate star cluster evolution in merging galaxies, determining their mass loss rates and lifetimes. In order to model this evolution, we have developed a second-order accurate numerical method for integrating a star cluster in an arbitrary, time-variable tidal field. We obtain realistic tidal histories from a galaxy merger simulation including sink particles, which we interpret as young star clusters. Coupling those tidal accelerations to N-body models of isolated clusters, we perform detailed dynamical studies. We extend the Kira N-body integrator to handle these external fields. This generalizes the formalism previously used to explore the dynamical effects of the galactic tidal field on clusters in circular orbits. Furthermore, we develop an effective semi-analytic model that can be used for fast estimation of cluster mass loss in a galactic tidal field. We use this model to study the evolution of globular cluster mass function in isolated and merging galaxies.