The script above was created to run as stand alone script, but if you have your table in you TOC, you can simply take the code below:
with arcpy.da.UpdateCursor('NombreDeLaTabla', ('Hora__GPS', 'Dia', 'Hora')) as curs:
for row in curs:
curs.updateRow((row[0], row[0].weekday() + 1, row[0].strftime('%H'), ))
... change the 'NombreDeLaTabla' on the first line into the name of your table, open the Python Window:
... paste the code:
.. and hit Enter.
(Check and change the names of the fields 'Hora__GPS', 'Dia', 'Hora' if your schema is different.)