Excel Date Field Import Problem in Oracle SQL Developer

You likely need to change your SQL Developer settings.

Tools->Preferences->Database->NLS

Modify the Timestamp Format field to conform to the data format in your Excel spreadsheet. Not how it appears in the first database, but what it looks like in your spreadsheet. For example, in my instance, the data in Excel was:

ID  DT
1   05/19/2011 10:16 PM

I changed the format in preferences to MM/DD/YYYY HH:MI AM

and was able to import successfully, after initially getting the same error you reported before changing preferences.

You may want to change the way your data is imported into Excel originally if you need more precision from your time values.

During the import wizard process (column definition screen), select the date type field on the left panel under 'Source Data Columns' and type in the expected format in the 'Format' text field. For example, MM/DD/YYYY or whatever the date format is in your import file for that field.