<sect2 id="calc-equinox">
<title>Equinoxes and Solstices module</title>
<indexterm><primary>Tools</primary>
<secondary>Astrocalculator</secondary>
<tertiary>Equinoxes and Solstices module</tertiary>
</indexterm>

<screenshot>
<screeninfo>
The Equinoxes and Solstices calculator module
</screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="calc-equinox.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase>Equinoxes and Solstices</phrase>
  </textobject>
</mediaobject>
</screenshot>

<para>
The <link linkend="ai-equinox">Equinoxes</link> and 
Solstices module calculates the date and time of an 
equinox or solstice for a given year.  You specify which 
event (Spring Equinox, Summer Solstice, Autumn Equinox, 
or Winter Solstice) should be investigated, and the year.  
Then press the <guibutton>Compute</guibutton> button to 
obtain the date and time of the event, and the length of 
the corresponding season, in days.
</para>
<para>
There is a batch mode for this module.  To use it, simply 
generate an input file whose lines each contain a year 
for which the Equinox and Solstice data will be computed.  
Then specify the input and output filenames, and press the 
<guibutton>Run</guibutton> button to generate the output 
file.  Each line in the output file contains the input year, 
the date and time of each event, and the length of each 
season.
</para>
</sect2>
