Oracle/PHP syntax to grab and later store a timestamp value in a date field

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There is a composite primary key stored in a DB that consists of a date field and a foreign key ID. Normally this would create duplicates however the date field (although it only displays the day, month, year appears to have timestamp information stored as well)My question is how to extract the timestamp information (I think using the to_char field) and more importantly, how I can later insert a record and store the date and timestamp.Right now I can store a date but not sure the syntax I would need to use to add the time to the Date field insert so it can be consistent with the values I pull from a table select.