Index: kosmorrolib/core.py
--- kosmorrolib/core.py.orig
+++ kosmorrolib/core.py
@@ -22,7 +22,18 @@ from skyfield.nutationlib import iau2000b
 
 from skyfield_data import get_skyfield_data_path
 
-LOADER = Loader(get_skyfield_data_path())
+# disable runtime warnings; skyfield-data warns if either of the data files
+# have expired when using get_skyfield_data_path, even if we're only actually
+# interested in de421 which expires in 2053.
+#
+# it is documented as supporting "Loader(get_skyfield_data_path(),
+# expire=False)" but that doesn't actually work.
+#
+import warnings
+
+with warnings.catch_warnings():
+    warnings.simplefilter("ignore")
+    LOADER = Loader(get_skyfield_data_path())
 
 
 def get_timescale():
