what you need to understand is that both dates and timestamps are internally stored as numbers - a value of the number of days and fractional days since a specific point in time. if used in a query, they are to_char() automatically with a certain format, if inserted, they are to_date() or to_timestamp() also with that certain format. I dont know if enough of the internals are revealed to e.g. allow you to insert the number 1.5 into a date column (thereby giving you a date that is 1.5 days after the epoch) so all insertion into, modification of and selection from date and time type columns must be done with sending in a representation of the time in format X and addionally a description of that format X in oracle compliant formatting