Hi, there seems to be a limitation for Python-based loader functions wrt timestamps. Looking at the implementation in sql/backends/monet5/UDF/pyapi3/convert_loops.h suggests that timestamps are indeed not covered. Both of the the 2 following examples fail with "Failed conversion: MALException:pyapi3.eval:PY000!Unrecognized type. Could not convert to NPY_UNICODE.". CREATE LOADER array_loader() LANGUAGE PYTHON { from datetime import datetime _emit.emit( { 'a': [1,2,3], 'b': [datetime.utcnow(), datetime.utcnow(), datetime.utcnow()], 'c': ['1', '2', '3']}) }; CREATE LOADER array_loader() LANGUAGE PYTHON { import numpy as np from datetime import datetime dt = datetime.utcnow() _emit.emit( { 'a': [1,2,3], 'b': np.array([dt, dt, dt], dtype=np.datetime64), 'c': ['1', '2', '3']}) }; Is anyone aware of a workaround? An obvious workaround is to insert the timestamps as strings and convert them via SQL but that's much less efficient. Kind regards, Daniel