BGP routing updates collected by monitoring projects such as RouteViews and RIPE have been a vital source to our understanding of the global routing system. The updates logged by these monitoring projects are generated either by individual route changes, or are part of BGP table transfer. In particular, a session reset between a monitoring station and its BGP peers can result in the peer sending its entire BGP routing table to the monitoring station. In this paper, we present a Minimum Collection Time (MCT) algorithm that accurately identify the start and duration of routing table transfers. Using three months of data from 14 different peers, MCT can identify routing table transfers triggered by BGP session resets with 100% accuracy, and can pinpoint the exact starting time of table transfers in 90% of the cases.