Document new cal-day procedures and add more tests.

doc/calendar.md

@@ -333,6 +333,56 @@ Parses the string and returns a valid cal-day structure.
 Tries parsing the string as cal-day and returns the result upon
 success. Upon failure, parses the string as cal-month.
 
+    (cal-day=? a b)
+
+* ```a``` - a cal-day value
+* ```b``` - a cal-day value
+
+Returns ```#t``` if ```a``` respresents the same date as ```b``` in
+calendar.
+
+    (cal-day<? a b)
+
+* ```a``` - a cal-day value
+* ```b``` - a cal-day value
+
+Returns ```#t``` if ```a``` comes before ```b``` in calendar.
+
+    (cal-day<=? a b)
+
+* ```a``` - a cal-day value
+* ```b``` - a cal-day value
+
+Returns ```#t``` if ```a``` comes before or is the same date as
+```b``` in calendar.
+
+    (cal-day>=? a b)
+
+* ```a``` - a cal-day value
+* ```b``` - a cal-day value
+
+Returns ```#t``` if ```a``` comes after or is the same date as ```b```
+in calendar.
+
+    (cal-day>? a b)
+
+Returns ```#t``` if ```a``` comes after ```b``` in calendar.
+
+    (cal-day/month<? a b)
+
+* ```a``` - a cal-day or cal-month value
+* ```b``` - a cal-day or cal-month value
+
+Returns ```#t``` if ```a``` and ```b``` are of the same type and
+```a``` comes before ```b``` in calendar. Raises error if the values
+are not of the same type.
+
+    (cal-day/month->string v)
+
+* ```v``` - a cal-day or cal-month value
+
+Returns appropriate string representation of given value.
+
 ### Format
 
     (import cal-format)