Techniques are provided to quickly estimate a temporal shift of a GPS signal based on an analysis of a GLONASS signal. The shift can be a result of applied leap-second adjustments affecting GLONASS signals but not GPS signals. By identifying this shift, GPS and GLONASS signals can be considered together in order to estimate locations. The temporal shift can be determined, e.g., by estimating a separation between a GPS-signal frame feature (e.g., frame onset) and a GLONASS-signal frame feature (e.g., frame onset), or identifying coinciding frame features (e.g., a GPS-signal subframe coinciding with a GLONASS-signal string number). The techniques allow the temporal shift to be estimated based on an analysis of just a portion of the GPS-signal and GLONASS-signal frames, such that a speed of location estimations can be improved.