PostgreSQL uses an internal heuristic parser for all date/time
input support. Dates and times are input as strings, and are
broken up into distinct fields with a preliminary determination
of what kind of information can be in the field. Each field is
interpreted and either assigned a numeric value, ignored, or
rejected. The parser contains internal lookup tables for all
textual fields, including months, days of the week, and time
zones. This appendix includes information on the content of
these lookup tables and describes the steps used by the parser
to decode dates and times.