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<chapter id="datatype">

</thead>

<tbody>

<row>

<entry><type>timestamp [ (<replaceable>p</replaceable>) ] without time zone</type></entry>

<entry><type>timestamp [ (<replaceable>p</replaceable>) ][without time zone ]</type></entry>

<entry>both date and time</entry>

<entry>8 bytes</entry>

<entry>4713 BC</entry>

<entry>AD 1465001</entry>

<entry>1 microsecond / 14 digits</entry>

</row>

<row>

<entry><type>timestamp [ (<replaceable>p</replaceable>) ][with time zone ]</type></entry>

<entry><type>timestamp [ (<replaceable>p</replaceable>) ] with time zone</type></entry>

<entry>both date and time</entry>

<entry>8 bytes</entry>

<entry>4713 BC</entry>

</row>

<row>

<entry><type>interval [ (<replaceable>p</replaceable>) ]</type></entry>

<entry>fortime intervals</entry>

<entry>time intervals</entry>

<entry>12 bytes</entry>

<entry>-178000000 years</entry>

<entry>178000000 years</entry>

optional precision value <replaceable>p</replaceable> which

specifies the number of fractional digits retained in the seconds

field. By default, there is no explicit bound on precision. The

effective limit of precision is determined by the underlying double

precision floating-point number used to store values (in seconds

for <type>interval</type> and

in seconds since 2000-01-01 for <type>timestamp</type>). The

useful range of <replaceable>p</replaceable> is from 0 to about

6 for <type>timestamp</type>, but may be more for <type>interval</type>.

The system will accept <replaceable>p</replaceable> ranging from

0 to 13.

allowed range of <replaceable>p</replaceable> is from 0 to 6.

</para>

<note>

<para>

When timestamps are stored as double precision floating-point

numbers (currently the default), the effective limit of precision

may be less than 6, since timestamp values are stored as seconds

since 2000-01-01. Microsecond precision is achieved for dates within

a few years of 2000-01-01, but the precision degrades for dates further

away. When timestamps are stored as eight-byte integers (a compile-time

option), microsecond precision is available over the full range of

values.

</para>

</note>

<para>

Time zones, and time-zone conventions, are influenced by

political decisions, not just earth geometry. Time zones around the