fixing issue where netCDF4.num2date throws ValueError when using time_offset variable

nc2csv.py

@@ -447,6 +447,14 @@ def process_one_file(variables: list, datastream: str, out_dir: str,
             except OverflowError as ofe:
                 nc2csv_logger.warning("{}: {} skipped.".format(ofe, file_name))
                 return None
+            except TypeError as te:
+                try:
+                    df["date_time"] = netCDF4.num2date(rootgrp.variables['time'][:],
+                                                   rootgrp.variables['time'].units,
+                                                       calendar='standard')
+                except Exception as e:
+                    nc2csv_logger.warning("{}: {} skipped.".format(e, file_name))
+                    return None
             nc2csv_logger.debug("created date_time column")
             # Set the new column as the index so we can do date based slicing for dqr filtering later.
             df.set_index("date_time", inplace=True)