diff --git a/circuitpython/code/cameteo.py b/circuitpython/code/cameteo.py
index ff1f0b8..3921e30 100644
--- a/circuitpython/code/cameteo.py
+++ b/circuitpython/code/cameteo.py
@@ -328,7 +328,7 @@ class GPSData(Data):
     def __init__(self, name="GPS",
                  update_interval=0, write_interval=60, send_interval=60,
                  enable=True, enable_pin=DigitalInOut(board.A5),
-                 rtc=None, debug=False):
+                 debug=False):
 
         Data.__init__(self, name=name,
                       update_interval=update_interval,
@@ -342,7 +342,6 @@ class GPSData(Data):
                      'alt': float(),
                      'qual': int(),
                      'age': int()}
-        self._rtc = rtc
         self._enable = enable
         self._gps_last_fix = int()
         self._gps_current_fix = int()
@@ -370,8 +369,6 @@ class GPSData(Data):
                 self._gps.timestamp_utc.tm_hour,
                 self._gps.timestamp_utc.tm_min,
                 self._gps.timestamp_utc.tm_sec)
-            if self._rtc is not None:
-                set_clock_from_localtime(self._rtc)
             if self._gps.has_fix:
                 self._gps_last_fix = self._gps_current_fix
                 self.data['lat'] = self._gps.latitude
@@ -397,25 +394,23 @@ class GPSData(Data):
             self._gps.send_command('PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0')
             self._gps.send_command('PMTK220,1000')    # 1000 ms refresh rate
 
-            if self._rtc is not None:
-                rtc.set_time_source(self._rtc)
-                if self.debug:
-                    print("GPS is the time source!")
-
     def disable(self):
         """Disable GPS module"""
         if self._enable:
             self._enable = False
             self._gps_en_pin.value = not self._enable  # Set enable pin high to disable GPS module
-            # Switch backto internal RTC
-            rtc.set_time_source(rtc.RTC())
+
+    @property
+    def datetime(self):
+        """Wrapper to feed rtc.set_time_source()"""
+        return self._gps.timestamp_utc
 
 
 #############
 # Functions #
 #############
 
-def set_clock_from_localtime(clock, treshold=2.0):
+def set_clock_from_localtime(clock, threshold=2.0, debug=False):
     """
     Compare internal RTC and date-time from time.localtime() and set
     the RTC date/time to this value if the difference is more or equal to
@@ -423,9 +418,24 @@ def set_clock_from_localtime(clock, treshold=2.0):
     The source of time.localtime() can be set with rtc.set_time_source()
     """
 
+    if debug:
+        print("Clock date/time : " + TIME_FORMAT.format(*clock.datetime[0:6]))
+        print("Local date/time : " + TIME_FORMAT.format(*time.localtime()[0:6]))
+
+    # Check if time.localtime() is valid and can be converted in seconds
+    try:
+        local_seconds = time.mktime(time.localtime())
+    except OverflowError as err:
+        print(err)
+        print("Local time source : " + TIME_FORMAT.format(*time.localtime()[0:6]))
+        print("Wait some time to have proper time from time source...")
+        return 1
+
     # Max difference between GPS and internal RTC (in seconds):
-    if abs(time.mktime(time.localtime()) - time.mktime(clock.datetime)) >= treshold:
-        # print("Clock difference with GPS!")
-        # print("Previous date/time : " + TIME_FORMAT.format(*clock.datetime[0:6]))
+    if abs(local_seconds - time.mktime(clock.datetime)) >= threshold:
+        print("Clock difference with GPS!")
+        print("Previous date/time : " + TIME_FORMAT.format(*clock.datetime[0:6]))
         clock.datetime = time.localtime()  # Trust localtime if there is a bias
         print("Clocks synced !")
+
+    return 0
diff --git a/circuitpython/code/main.py b/circuitpython/code/main.py
index 6b0ddad..59b6faa 100644
--- a/circuitpython/code/main.py
+++ b/circuitpython/code/main.py
@@ -91,10 +91,12 @@ else:
 
 sys_data = cameteo.SysData(debug=False)
 bme_data = cameteo.BME280Data()
-gps_data = cameteo.GPSData(rtc=CLOCK)
+gps_data = cameteo.GPSData()
 
 data = [gps_data, sys_data, bme_data]
 
+rtc.set_time_source(gps_data, debug=True)
+
 # Init timers
 last_update = last_sent_packet = last_written_data = time.monotonic()
 
@@ -108,6 +110,7 @@ while True:
 
     for src in data:
         src.update(current_time, verbose=PRINT_DATA)
+        cameteo.set_clock_from_localtime(CLOCK, threshold=2.0)
 
     for src in data:
         src.write_on_flash(current_time)