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Appendix A. Date/Time Support

Table of Contents
A.1. Date/Time Keywords
A.2. Time Zones
A.3. History of Units

PostgreSQL uses an internal heuristic parser for all date/time support. Dates and times are input as strings, and are broken up into distinct fields with a preliminary determination of what kind of information may 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.

A.1. Date/Time Keywords

Table A-1. Month Abbreviations

MonthAbbreviations
AprilApr
AugustAug
DecemberDec
FebruaryFeb
JanuaryJan
JulyJul
JuneJun
MarchMar
NovemberNov
OctoberOct
SeptemberSep, Sept

Note: The month May has no explicit abbreviation, for obvious reasons.

Table A-2. Day of the Week Abbreviations

DayAbbreviation
SundaySun
MondayMon
TuesdayTue, Tues
WednesdayWed, Weds
ThursdayThu, Thur, Thurs
FridayFri
SaturdaySat

Table A-3. PostgreSQL Field Modifiers

IdentifierDescription
ABSTIMEKeyword ignored
AMTime is before 12:00
ATKeyword ignored
JULIAN, JD, JNext field is Julian Day
ONKeyword ignored
PMTime is on or after after 12:00
TNext field is time

The keyword ABSTIME is ignored for historical reasons; in very old releases of PostgreSQL invalid ABSTIME fields were emitted as Invalid Abstime. This is no longer the case however and this keyword will likely be dropped in a future release.