How to reference the official oracle documentation?
Abstract concepts such as datetime or longs are generally not attributed to Oracle or similar companies, if anything you should cite an earlier work that discusses and introduces the concepts. The earliest mention that I know that introduces most of these concepts that are used in many (if not all) modern databases and programming languages derive from C, it even introduced us to the Hello World concept. Therefore a good reference would be:


  Kernighan, B. W., &amp; Ritchie, D. M. (1978). The C programming language.
  Prentice-Hall, Inc. Upper Saddle River, NJ, USA (ISBN: 0-13-110163-3).


Co-incidentally, according to Google Scholar this work has been referenced 8000+ times as of the 4th of December, 2018.

PS: There may be earlier references of specific datatypes, but I argue that no other work has brought them all together in one place before the work of Kernighan and Ritchie.