timestamp from another one and save the result in a
        variable of type interval.
<synopsis>
int PGTYPEStimestamp_sub(timestamp *ts1, timestamp *ts2, interval *iv);
</synopsis>
        The function will subtract the timestamp variable that <literal>ts2</literal>
        points to from the timestamp variable that <literal>ts1</literal> points to
        and will store the result in the interval variable that <literal>iv</literal>
        points to.
       </para>
       <para>
        Upon success, the function returns 0 and a negative value if an
        error occurred.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="pgtypestimestampdefmtasc">
      <term><function>PGTYPEStimestamp_defmt_asc</function></term>
      <listitem>
       <para>
        Parse a timestamp value from its textual representation using a
        formatting mask.
<synopsis>
int PGTYPEStimestamp_defmt_asc(char *str, char *fmt, timestamp *d);
</synopsis>
        The function receives the textual representation of a timestamp in the
        variable <literal>str</literal> as well as the formatting mask to use in the
        variable <literal>fmt</literal>. The result will be stored in the variable
        that <literal>d</literal> points to.
       </para>
       <para>
        If the formatting mask <literal>fmt</literal> is NULL, the function will fall
        back to the default formatting mask which is <literal>%Y-%m-%d
        %H:%M:%S</literal>.
       </para>
       <para>
        This is the reverse function to <xref
        linkend="pgtypestimestampfmtasc"/>.  See the documentation there in
        order to find out about the possible formatting mask entries.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="pgtypestimestampaddinterval">
      <term><function>PGTYPEStimestamp_add_interval</function></term>
      <listitem>
       <para>
        Add an interval variable to a timestamp variable.
<synopsis>
int PGTYPEStimestamp_add_interval(timestamp *tin, interval *span, timestamp *tout);
</synopsis>
        The function receives a pointer to a timestamp variable <literal>tin</literal>
        and a pointer to an interval variable <literal>span</literal>. It adds the
        interval to the timestamp and saves the resulting timestamp in the
        variable that <literal>tout</literal> points to.
       </para>
       <para>
        Upon success, the function returns 0 and a negative value if an
        error occurred.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="pgtypestimestampsubinterval">
      <term><function>PGTYPEStimestamp_sub_interval</function></term>
      <listitem>
       <para>
        Subtract an interval variable from a timestamp variable.
<synopsis>
int PGTYPEStimestamp_sub_interval(timestamp *tin, interval *span, timestamp *tout);
</synopsis>
        The function subtracts the interval variable that <literal>span</literal>
        points to from the timestamp variable that <literal>tin</literal> points to
        and saves the result into the variable that <literal>tout</literal> points
        to.
       </para>
       <para>
        Upon success, the function returns 0 and a negative value if an
        error occurred.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </sect2>

  <sect2 id="ecpg-pgtypes-interval">
   <title>The interval Type</title>
   <para>
    The interval type in C enables your programs to deal with data of the SQL
    type interval. See <xref linkend="datatype-datetime"/> for the equivalent
    type in the <productname>PostgreSQL</productname> server.
   </para>
   <para>
    The following functions can be used to work with the interval type:
    <variablelist>

     <varlistentry id="pgtypesintervalnew">
      <term><function>PGTYPESinterval_new</function></term>
      <listitem>
       <para>
        Return a pointer to a newly allocated interval variable.
<synopsis>
interval *PGTYPESinterval_new(void);