Australian time zones and their naming variants account for fully one quarter of all time zones in the Postgres time zone lookup table. Dates are stored internally in Greenwich Mean Time. Input and output routines translate time to the local time zone of the server. For date arithmetic, the qualitative time units are instantiated in the context of the relevant date or time. Unit is second , minute , hour , day , week , month , year , decade , century , millenium , or abbreviations or plurals of these units.
Direction is ago .
Instead, reltime must force months to be exactly 30 days, so time arithmetic does not always work as expected. For example, adding one reltime year to abstime today does not produce today's date one year from now, but rather a date 360 days from today. The section on timespan covers this in more detail. This is currently a limited-range absolute time which closely resembles the abstime data type. In future releases this type will absorb the capabilities of the datetime type and will move toward SQL92 compliance.