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<chapter id="datatype">

</para>

<para>

The optional precision

<replaceable>p</replaceable> should be between 0 and 6, and

defaults to the precision of the input literal.

The optional subsecond precision <replaceable>p</replaceable> should

be between 0 and 6, and defaults to the precision of the input literal.

</para>

<para>

Internally <type>interval</> values are stored as months, days,

and seconds. This is done because the number of days in a month

varies, and a day can have 23 or 25 hours if a daylight savings

time adjustment is involved. Because intervals are usually created

from constant strings or <type>timestamp</> subtraction, this

storage method works well in most cases. Functions

<function>justify_days</> and <function>justify_hours</> are

available for adjusting days and hours that overflow their normal

periods.

</para>

</sect3>

<literal>CURRENT_DATE</literal>, <literal>CURRENT_TIME</literal>,

<literal>CURRENT_TIMESTAMP</literal>, <literal>LOCALTIME</literal>,

<literal>LOCALTIMESTAMP</literal>. The latter four accept an

optional precision specification. (See <xref

optionalsubsecondprecision specification. (See <xref

linkend="functions-datetime-current">.) Note however that these are

SQL functions and are <emphasis>not</> recognized as data input strings.

</para>