diff --git a/reference/calendar/constants.xml b/reference/calendar/constants.xml
index 7e3029af98..fa9d3a0307 100644
--- a/reference/calendar/constants.xml
+++ b/reference/calendar/constants.xml
@@ -11,7 +11,9 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>easter_days</function>: calculate Easter for years before
+     1753 according to the Julian calendar, and for later years according to the
+     Gregorian calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -22,7 +24,9 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>easter_days</function>: calculate Easter for years before
+     1583 according to the Julian calendar, and for later years according to the
+     Gregorian calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -33,7 +37,8 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>easter_days</function>: calculate Easter according to the
+     proleptic Gregorian calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -44,7 +49,8 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>easter_days</function>: calculate Easter according to the
+     Julian calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -55,7 +61,9 @@
    </term>
    <listitem>
     <simpara>
-
+     For <function>cal_days_in_month</function>,
+     <function>cal_from_jd</function>, <function>cal_info</function> and
+     <function>cal_to_jd</function>: use the proleptic Gregorian calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -66,7 +74,9 @@
    </term>
    <listitem>
     <simpara>
-
+     For <function>cal_days_in_month</function>,
+     <function>cal_from_jd</function>, <function>cal_info</function> and
+     <function>cal_to_jd</function>: use the Julian calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -77,7 +87,9 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>cal_days_in_month</function>,
+     <function>cal_from_jd</function>, <function>cal_info</function> and
+     <function>cal_to_jd</function>: use the Jewish calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -88,7 +100,8 @@
    </term>
    <listitem>
     <simpara>
-
+     For <function>jdtojewish</function>: adds a geresh symbol (which resembles
+     a single-quote mark) as thousands separator to the year number.
     </simpara>
    </listitem>
   </varlistentry>
@@ -99,7 +112,8 @@
    </term>
    <listitem>
     <simpara>
-
+     For <function>jdtojewish</function>: adds the word alafim as thousands
+     separator to the year number.
     </simpara>
    </listitem>
   </varlistentry>
@@ -110,7 +124,8 @@
    </term>
    <listitem>
     <simpara>
-
+     For <function>jdtojewish</function>: add a gershayim symbol (which
+     resembles a double-quote mark) before the final letter of the day and year numbers.
     </simpara>
    </listitem>
   </varlistentry>
@@ -121,7 +136,9 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>cal_days_in_month</function>,
+     <function>cal_from_jd</function>, <function>cal_info</function> and
+     <function>cal_to_jd</function>: use the French Repuclican calendar.
     </simpara>
    </listitem>
   </varlistentry>
@@ -132,7 +149,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     The number of available calendars.
     </simpara>
    </listitem>
   </varlistentry>
@@ -143,7 +160,9 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jddayofweek</function>: the day of the week as
+     <type>integer</type>, where <literal>0</literal> means Sunday and
+     <literal>6</literal> means Saturday.
     </simpara>
    </listitem>
   </varlistentry>
@@ -154,7 +173,8 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jddayofweek</function>: the abbreviated English name of the
+     day of the week.
     </simpara>
    </listitem>
   </varlistentry>
@@ -165,7 +185,8 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jddayofweek</function>: the English name of the day of the
+     week.
     </simpara>
    </listitem>
   </varlistentry>
@@ -176,7 +197,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jdmonthname</function>: the abbreviated Gregorian month name.
     </simpara>
    </listitem>
   </varlistentry>
@@ -187,7 +208,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jdmonthname</function>: the Gregorian month name.
     </simpara>
    </listitem>
   </varlistentry>
@@ -198,7 +219,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jdmonthname</function>: the abbreviated Julian month name.
     </simpara>
    </listitem>
   </varlistentry>
@@ -209,7 +230,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jdmonthname</function>: the Julian month name.
     </simpara>
    </listitem>
   </varlistentry>
@@ -220,7 +241,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jdmonthname</function>: the Jewish month name.
     </simpara>
    </listitem>
   </varlistentry>
@@ -231,7 +252,7 @@
    </term>
    <listitem>
     <simpara>
-     
+     For <function>jdmonthname</function>: the French Republican month name.
     </simpara>
    </listitem>
   </varlistentry>