diff --git a/circuitpython/code/main.py b/circuitpython/code/main.py
index a8f598f..71181b7 100644
--- a/circuitpython/code/main.py
+++ b/circuitpython/code/main.py
@@ -245,6 +245,33 @@ def check_data_dir():
         # Turn onboard led on to indicate read-only error
         led13.value = True
 
+def rotate_files():
+    """Check if files need to rotate
+    => every new hour
+    => every new day
+    """
+    global last_time
+    current_time = clock.datetime
+
+    #If the hour changed : copy current data.csv to hourly directory
+    if current_time[3] != last_time[3] and backup_data:
+        print("Time to move hourly data !")
+        os.rename("data/data.csv", "data/hourly/{}.csv".format(last_time[3]))
+
+    #If the day changed : copy content of hourly to daily directories
+    if current_time[2] != last_time[2] and backup_data:
+        print("Time to move daily data !")
+        #Create new dir for the date of yesterday
+        newdir = "data/daily/{}{}{}.csv".format(last_time[0:2])
+        os.mkdir(newdir)
+        #Move each "hourly file" to the new directory
+        for file in os.listdir('data/hourly'):
+            print("Move {} to {}".format(newdir, file))
+            os.rename("data/hourly/{}".format(file), "{}/{}".format(newdir, file))
+
+    #Finally update last_time, each time
+    last_time = current_time
+
 
 def set_clock_from_GPS(treshold=5.0):
     """Compare internal RTC and date-time from GPS (if enable and fixed) and set
@@ -347,6 +374,8 @@ data = Data()
 
 #Init timer
 last_update = last_sent_packet = last_written_data =  time.monotonic()
+last_time = clock.datetime
+
 while True:
 
     if gps_enable:
@@ -369,6 +398,7 @@ while True:
 
     if backup_data and current - last_written_data >= write_interval :
         last_written_data = current
+        rotate_files()              #First check if files need to rotate
         print("Backup data...")
         data.write_on_flash()