diff --git a/src/drivers/gps/ashtech.cpp b/src/drivers/gps/ashtech.cpp
index 99dbe5984f..a50767c22c 100644
--- a/src/drivers/gps/ashtech.cpp
+++ b/src/drivers/gps/ashtech.cpp
@@ -99,21 +99,26 @@ int ASHTECH::handle_message(int len)
 		timeinfo.tm_sec = int(ashtech_sec);
 		time_t epoch = mktime(&timeinfo);
 
-		uint64_t usecs = static_cast<uint64_t>((ashtech_sec - static_cast<uint64_t>(ashtech_sec))) * 1e6;
+		if (epoch > GPS_EPOCH_SECS) {
+			uint64_t usecs = static_cast<uint64_t>((ashtech_sec - static_cast<uint64_t>(ashtech_sec))) * 1e6;
 
-		// FMUv2+ boards have a hardware RTC, but GPS helps us to configure it
-		// and control its drift. Since we rely on the HRT for our monotonic
-		// clock, updating it from time to time is safe.
+			// FMUv2+ boards have a hardware RTC, but GPS helps us to configure it
+			// and control its drift. Since we rely on the HRT for our monotonic
+			// clock, updating it from time to time is safe.
 
-		timespec ts;
-		ts.tv_sec = epoch;
-		ts.tv_nsec = usecs * 1000;
-		if (clock_settime(CLOCK_REALTIME, &ts)) {
-			warn("failed setting clock");
+			timespec ts;
+			ts.tv_sec = epoch;
+			ts.tv_nsec = usecs * 1000;
+			if (clock_settime(CLOCK_REALTIME, &ts)) {
+				warn("failed setting clock");
+			}
+
+			_gps_position->time_utc_usec = static_cast<uint64_t>(epoch) * 1000000ULL;
+			_gps_position->time_utc_usec += usecs;
+		} else {
+			_gps_position->time_utc_usec = 0;
 		}
 
-		_gps_position->time_utc_usec = static_cast<uint64_t>(epoch) * 1000000ULL;
-		_gps_position->time_utc_usec += usecs;
 		_gps_position->timestamp_time = hrt_absolute_time();
 	}
 
diff --git a/src/drivers/gps/gps_helper.h b/src/drivers/gps/gps_helper.h
index 3623397b2d..0ce05fcb50 100644
--- a/src/drivers/gps/gps_helper.h
+++ b/src/drivers/gps/gps_helper.h
@@ -43,6 +43,8 @@
 #include <uORB/uORB.h>
 #include <uORB/topics/vehicle_gps_position.h>
 
+#define GPS_EPOCH_SECS 1234567890ULL
+
 class GPS_Helper
 {
 public:
diff --git a/src/drivers/gps/ubx.cpp b/src/drivers/gps/ubx.cpp
index 05809b3617..e197059db1 100644
--- a/src/drivers/gps/ubx.cpp
+++ b/src/drivers/gps/ubx.cpp
@@ -748,19 +748,23 @@ UBX::payload_rx_done(void)
 			timeinfo.tm_sec		= _buf.payload_rx_nav_pvt.sec;
 			time_t epoch = mktime(&timeinfo);
 
-			// FMUv2+ boards have a hardware RTC, but GPS helps us to configure it
-			// and control its drift. Since we rely on the HRT for our monotonic
-			// clock, updating it from time to time is safe.
+			if (epoch > GPS_EPOCH_SECS) {
+				// FMUv2+ boards have a hardware RTC, but GPS helps us to configure it
+				// and control its drift. Since we rely on the HRT for our monotonic
+				// clock, updating it from time to time is safe.
 
-			timespec ts;
-			ts.tv_sec = epoch;
-			ts.tv_nsec = _buf.payload_rx_nav_pvt.nano;
-			if (clock_settime(CLOCK_REALTIME, &ts)) {
-				warn("failed setting clock");
+				timespec ts;
+				ts.tv_sec = epoch;
+				ts.tv_nsec = _buf.payload_rx_nav_pvt.nano;
+				if (clock_settime(CLOCK_REALTIME, &ts)) {
+					warn("failed setting clock");
+				}
+
+				_gps_position->time_utc_usec = static_cast<uint64_t>(epoch) * 1000000ULL;
+				_gps_position->time_utc_usec += _buf.payload_rx_nav_timeutc.nano / 1000;
+			} else {
+				_gps_position->time_utc_usec = 0;
 			}
-
-			_gps_position->time_utc_usec = static_cast<uint64_t>(epoch) * 1000000ULL;
-			_gps_position->time_utc_usec += _buf.payload_rx_nav_timeutc.nano / 1000;
 		}
 
 		_gps_position->timestamp_time		= hrt_absolute_time();
@@ -820,19 +824,25 @@ UBX::payload_rx_done(void)
 			timeinfo.tm_sec		= _buf.payload_rx_nav_timeutc.sec;
 			time_t epoch = mktime(&timeinfo);
 
-			// FMUv2+ boards have a hardware RTC, but GPS helps us to configure it
-			// and control its drift. Since we rely on the HRT for our monotonic
-			// clock, updating it from time to time is safe.
+			// only set the time if it makes sense
 
-			timespec ts;
-			ts.tv_sec = epoch;
-			ts.tv_nsec = _buf.payload_rx_nav_timeutc.nano;
-			if (clock_settime(CLOCK_REALTIME, &ts)) {
-				warn("failed setting clock");
+			if (epoch > GPS_EPOCH_SECS) {
+				// FMUv2+ boards have a hardware RTC, but GPS helps us to configure it
+				// and control its drift. Since we rely on the HRT for our monotonic
+				// clock, updating it from time to time is safe.
+
+				timespec ts;
+				ts.tv_sec = epoch;
+				ts.tv_nsec = _buf.payload_rx_nav_timeutc.nano;
+				if (clock_settime(CLOCK_REALTIME, &ts)) {
+					warn("failed setting clock");
+				}
+
+				_gps_position->time_utc_usec = static_cast<uint64_t>(epoch) * 1000000ULL;
+				_gps_position->time_utc_usec += _buf.payload_rx_nav_timeutc.nano / 1000;
+			} else {
+				_gps_position->time_utc_usec = 0;
 			}
-
-			_gps_position->time_utc_usec = static_cast<uint64_t>(epoch) * 1000000ULL;
-			_gps_position->time_utc_usec += _buf.payload_rx_nav_timeutc.nano / 1000;
 		}
 
 		_gps_position->timestamp_time = hrt_absolute_time();