diff --git a/src/fsfw/coordinates/Sgp4Propagator.cpp b/src/fsfw/coordinates/Sgp4Propagator.cpp
index e79ffef5..62c2670e 100644
--- a/src/fsfw/coordinates/Sgp4Propagator.cpp
+++ b/src/fsfw/coordinates/Sgp4Propagator.cpp
@@ -166,9 +166,9 @@ ReturnValue_t Sgp4Propagator::propagate(double* position, double* velocity, time
   timeval timeSinceEpoch = time - epoch;
   double minutesSinceEpoch = timeSinceEpoch.tv_sec / 60. + timeSinceEpoch.tv_usec / 60000000.;
 
-  double yearsSinceEpoch = minutesSinceEpoch / 60 / 24 / 365;
+  double monthsSinceEpoch = minutesSinceEpoch / 60 / 24 / 30;
 
-  if ((yearsSinceEpoch > 1) || (yearsSinceEpoch < -1)) {
+  if ((monthsSinceEpoch > 1) || (monthsSinceEpoch < -1)) {
     return TLE_TOO_OLD;
   }