diff --git a/src/guitastro/dates.py b/src/guitastro/dates.py
index 06a7b73..58bfb88 100644
--- a/src/guitastro/dates.py
+++ b/src/guitastro/dates.py
@@ -1136,12 +1136,25 @@ class Date(GuitastroTools):
 
 if __name__ == "__main__":
 
-    example = 1
+    default = 1
+    example = input(f"Select the example (0 to 1) ({default}) ")
+    try:
+        example = int(example)
+    except:
+        example = default
     print("Example       = {}".format(example))
 
-    if example == 1:
+    if example == 0:
         """
-        Difference coord angles
+        Get current julian day
         """
         d = Date("now")
         print(f"Now: {d.iso()} JD={d.jd()}")
+
+    if example == 1:
+        """
+        Get ISO from julian day
+        """
+        d = Date(2456789.3456)
+        print(f"Now: {d.iso()} JD={d.jd()}")
+
diff --git a/src/guitastro/ephemeris.py b/src/guitastro/ephemeris.py
index 6701861..b42acdb 100644
--- a/src/guitastro/ephemeris.py
+++ b/src/guitastro/ephemeris.py
@@ -1193,7 +1193,7 @@ class Ephemeris(EphemerisException, GuitastroTools):
         relative_humidity = rel_humidity
         obswl = wavelength_nm * u.nm
         fn = FileNames()
-        fn.longitude(self.home.longitude)
+        fn.longitude = self.home.longitude
         # --- compute jd1, jd2 the limits of dates to compute the ephemeris
         if nsec == 86400:
             # - we compute ephemeris for all the night
diff --git a/src/guitastro/filenames.py b/src/guitastro/filenames.py
index 2f0e82e..9eb250c 100644
--- a/src/guitastro/filenames.py
+++ b/src/guitastro/filenames.py
@@ -161,7 +161,7 @@ class FileNames(FileNamesException, GuitastroTools):
     ::
 
         fn = FileNames()
-        fn.longitude(-90)
+        fn.longitude = -90
         night = "20230506"
         jd1, jd2 = fn.night2date(night)
 
@@ -174,12 +174,12 @@ class FileNames(FileNamesException, GuitastroTools):
     the method date2night() returns a string corresponding to the night
     directory according an input date (i.e. DATE-OBS). The method date2night()
     consider a night as from noon to noon. To do that, before using date2night()
-    you must specify the longitude of the observatory with the method longitude().
+    you must specify the longitude of the observatory with the attribute longitude.
 
     ::
 
         fn = FileNames()
-        fn.longitude(-90)
+        fn.longitude = -90
         date = "2023-06-12T23:02:45"
         night = fn.date2night(date)
 
@@ -350,6 +350,7 @@ class FileNames(FileNamesException, GuitastroTools):
         # --- naming_rule
         if len(args) > 0 :
             self.naming(args[0])
+        self.longitude = 0
 
     def __repr__(self):
         return str(self)
@@ -368,7 +369,10 @@ class FileNames(FileNamesException, GuitastroTools):
         msg += f"\nExtension: {self.extension}"
         return msg
 
-    def longitude(self, longiau_deg:float):
+    def _get_longitude(self):
+        return self._longiau_deg
+
+    def _set_longitude(self, longiau_deg:float):
         """ Set the longitude of the observation siteobs.
 
         This method is useful for the method get_night().
@@ -380,11 +384,13 @@ class FileNames(FileNamesException, GuitastroTools):
         ::
 
             ima1 = Ima()
-            ima1.longitude(2.3456)
+            ima1.longitude = 2.3456
 
         """
         self._longiau_deg = longiau_deg
 
+    longitude = property(_get_longitude, _set_longitude)
+
     # =============================================
     # Print filters
     # =============================================
@@ -2351,7 +2357,7 @@ class FileNames(FileNamesException, GuitastroTools):
 
             fn = FileNames()
             fn.pathing("YYYY/MM/DD")
-            fn.longitude(45.678)
+            fn.longitude = 45.678
             param = {}
             param['date'] = "2021-10-26T13:45:23"
             param['night'] = True
@@ -2507,7 +2513,7 @@ class FileNames(FileNamesException, GuitastroTools):
 
             fn = FileNames()
             fn.pathnaming("PyROS.img.1")
-            fn.longitude(45.678)
+            fn.longitude = 45.678
             date = "2021-10-26T13:45:23"
             fnd = fn.naming_date(date)
             pparam = {}
@@ -2645,7 +2651,7 @@ class FileNames(FileNamesException, GuitastroTools):
     def date2night(self, date: str="now", sampling: int=0)->str:
         """Get the current night identifier as a string of 8 characters: YYYYMMDD.
 
-        The night identifier changes at local noon. So it uses the longitude defined in longitude() method.
+        The night identifier changes at local noon. So it uses the longitude defined in longitude attribute.
 
         Args:
             date: Input date to compute the night identifier. Defaut value is "now".
@@ -2705,7 +2711,7 @@ class FileNames(FileNamesException, GuitastroTools):
     def night2date(self, night: str="now")->str:
         """Get the current julian day limits from a night identifier as a string of 8 characters: YYYYMMDD.
 
-        The night identifier changes at local noon. So it uses the longitude defined in longitude() method.
+        The night identifier changes at local noon. So it uses the longitude defined in longitude attribute.
 
         Args:
             date: The night identifier string YYYYMMDD or a date (default is "now").
@@ -2995,7 +3001,7 @@ class FileNames(FileNamesException, GuitastroTools):
         ::
 
             fn = FileNames()
-            fn.longitude(165.85944)
+            fn.longitude = 165.85944
             fn.fcontext_create("my_context", "Test")
             fn.fcontext = "my_context"
             fn.rootdir = "/tmp"
@@ -3896,7 +3902,7 @@ if __name__ == "__main__":
         fn = FileNames()
         fn.pathing("YYYY/MM/DD")
         params = fn.pathing_get("/tmp/2023/01/04")
-        fn.longitude(45.678)
+        fn.longitude = 45.678
         param = {}
         param['date'] = params['date']
         param['night'] = False
@@ -3906,7 +3912,7 @@ if __name__ == "__main__":
 
         fn = FileNames()
         fn.pathing("YYYY/YYYYMMDD")
-        fn.longitude(45.678)
+        fn.longitude = 45.678
         param = {}
         param['date'] = "2021-10-26T13:45:23"
         param['night'] = True
@@ -3917,7 +3923,7 @@ if __name__ == "__main__":
         """
         fn = FileNames()
         fn.pathnaming("PyROS.img.1")
-        fn.longitude(45.678)
+        fn.longitude = 45.678
         date = "2021-10-26T13:45:23"
         fnd = fn.naming_date(date)
         pparam = {}
@@ -3941,7 +3947,7 @@ if __name__ == "__main__":
         """
         fn = FileNames()
         fn.naming("T1M.1")
-        fn.longitude(45.678)
+        fn.longitude = 45.678
         date = "2021-10-26T13:45:23"
         fnd = fn.naming_date(date)
         fparam = {}
@@ -3974,7 +3980,7 @@ if __name__ == "__main__":
         """
         fn = FileNames()
         longitude= -90
-        fn.longitude(longitude)
+        fn.longitude = longitude
         print(f"longitude = {longitude}")
         # --- Define a date of the observation
         date = "2023-03-20T17:00:00"
@@ -3993,7 +3999,7 @@ if __name__ == "__main__":
         Get path from name
         """
         fn = FileNames()
-        fn.longitude(45.678)
+        fn.longitude = 45.678
         fn.fcontext = "image_raw"
         fn.pathnaming("PyROS.img.1")
         fn.rootdir = "/tmp"
@@ -4055,7 +4061,7 @@ if __name__ == "__main__":
         Manage many contexts for PyROS
         """
         fn = FileNames()
-        fn.longitude(165.85944)
+        fn.longitude = 165.85944
 
         # --- Create a file context for L0 images
         fn.fcontext_create("pyros_img_L0", "Images L0A")
--
libgit2 0.21.2