GLONASS nav message date setting uses GPS instead of UTC
The RINEX parsing code for GLONASS appears to construct a GNSS date based on the GPS system; however, section 8.1 of the RINEX documentation states
GLONASS is basically running on UTC (or, more precisely, GLONASS system time linked to UTC(SU)), i.e. the time tags are given in UTC and not GPS time. It is not a continuous time, i.e. it introduces the same leap seconds as UTC. The reported GLONASS time has the same hours as UTC and not UTC+3 h as the original GLONASS System Time!
Per discussion on https://forum.orekit.org/t/glonass-epoch-vs-gps-epoch/2283, suggested course of action is to pass "date" directly in to the "set" method and remove the construction of the GNSS date based on GPS epoch.