diff --git a/libraries/AP_GPS/AP_GPS_UBLOX.cpp b/libraries/AP_GPS/AP_GPS_UBLOX.cpp
index fd77f56dc3..d6762d82e9 100644
--- a/libraries/AP_GPS/AP_GPS_UBLOX.cpp
+++ b/libraries/AP_GPS/AP_GPS_UBLOX.cpp
@@ -28,6 +28,8 @@
 #include <GCS_MAVLink/GCS.h>
 #include "RTCM3_Parser.h"
 #include <stdio.h>
+#include <time.h>
+#include <AP_Common/time.h>
 
 #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_NAVIO || \
     CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BH
@@ -1580,6 +1582,7 @@ AP_GPS_UBLOX::_parse_gps(void)
         _check_new_itow(_buffer.solution.itow);
         if (havePvtMsg) {
             state.time_week = _buffer.solution.week;
+            _have_receiver_week = true;
             break;
         }
         if (_buffer.solution.fix_status & NAV_STATUS_FIX_VALID) {
@@ -1606,6 +1609,7 @@ AP_GPS_UBLOX::_parse_gps(void)
             state.last_gps_time_ms = AP_HAL::millis();
             state.time_week_ms    = _buffer.solution.itow;
             state.time_week       = _buffer.solution.week;
+            _have_receiver_week = true;
         }
 #if UBLOX_FAKE_3DLOCK
         next_fix = state.status;
@@ -1744,6 +1748,39 @@ AP_GPS_UBLOX::_parse_gps(void)
         
         // time
         state.time_week_ms    = _buffer.pvt.itow;
+
+        // RoboFusion patch: some UBX-compatible receivers (for example
+        // Unicore UM626N based modules) only output NAV-PVT and never send
+        // NAV-SOL or NAV-TIMEGPS, so time_week stays 0 and the vehicle never
+        // gets a valid GPS time. Until the receiver supplies the week itself,
+        // derive it from the PVT UTC date/time. The receiver's own iTOW is
+        // used as the reference and the result is rounded to the nearest
+        // week, so a leap-second or rounding offset cannot shift the week.
+        if (!_have_receiver_week &&
+            (_buffer.pvt.valid & 0x03) == 0x03 &&   // validDate and validTime
+            _buffer.pvt.year >= 2020 && _buffer.pvt.year < 2100 &&
+            _buffer.pvt.month >= 1 && _buffer.pvt.month <= 12 &&
+            _buffer.pvt.day >= 1 && _buffer.pvt.day <= 31) {
+            struct tm tm {};
+            tm.tm_year = _buffer.pvt.year - 1900;
+            tm.tm_mon  = _buffer.pvt.month - 1;
+            tm.tm_mday = _buffer.pvt.day;
+            tm.tm_hour = _buffer.pvt.hour;
+            tm.tm_min  = _buffer.pvt.min;
+            tm.tm_sec  = _buffer.pvt.sec;
+            const uint32_t unix_secs = uint32_t(ap_mktime(&tm));
+            const uint32_t unix_to_gps_secs = 315964800UL;
+            const uint32_t leap_secs = uint32_t(GPS_LEAPSECONDS_MILLIS / 1000U);
+            const uint32_t gps_secs = unix_secs + leap_secs - unix_to_gps_secs;
+            const uint32_t itow_secs = _buffer.pvt.itow / 1000U;
+            const uint32_t week = (gps_secs - itow_secs + AP_SEC_PER_WEEK / 2U) / AP_SEC_PER_WEEK;
+            state.time_week = uint16_t(week);
+            if (!_pvt_week_announced) {
+                _pvt_week_announced = true;
+                GCS_SEND_TEXT(MAV_SEVERITY_INFO, "u-blox %d: GPS week %u from NAV-PVT date",
+                              state.instance + 1, unsigned(week));
+            }
+        }
 #if UBLOX_FAKE_3DLOCK
         state.location.lng = 1491652300L;
         state.location.lat = -353632610L;
@@ -1765,6 +1802,7 @@ AP_GPS_UBLOX::_parse_gps(void)
         _check_new_itow(_buffer.timegps.itow);
         if (_buffer.timegps.valid & UBX_TIMEGPS_VALID_WEEK_MASK) {
             state.time_week = _buffer.timegps.week;
+            _have_receiver_week = true;
         }
         break;
     case MSG_VELNED:
diff --git a/libraries/AP_GPS/AP_GPS_UBLOX.h b/libraries/AP_GPS/AP_GPS_UBLOX.h
index 47d1ccbd3f..b83c5c398e 100644
--- a/libraries/AP_GPS/AP_GPS_UBLOX.h
+++ b/libraries/AP_GPS/AP_GPS_UBLOX.h
@@ -812,6 +812,12 @@ private:
     
     bool havePvtMsg;
 
+    // RoboFusion: true once the receiver itself has supplied the GPS week
+    // (NAV-SOL or NAV-TIMEGPS). Until then the week is derived from the
+    // NAV-PVT UTC date, for PVT-only receivers such as UM626N modules.
+    bool _have_receiver_week { false };
+    bool _pvt_week_announced { false };
+
     // structure for list of config key/value pairs for
     // specific configurations
     struct PACKED config_list {