Date format in oracle

It happens so because date format you are trying to insert in orcale database is not same as the Oracle date format (i.e. NLS_Date_Format).

You can find the Oracle date format using this query :

SELECT * from NLS_INSTANCE_PARAMETERS;

You can set the Oracle date format to any any pattern using :

Alter Session set NLS_Date_Format='MM/DD/YYYY'

Once you set the NLS_Date_Format in Oracle, use this format in vb when inserting data in oracle.

Hope this helps.
All the best.