Document new cal-period procedures.

doc/calendar.md

@@ -152,6 +152,12 @@ after the period.
 Configuration parameter specifying the current month. Defaults to the
 current month derived from the current system time.
 
+    (*current-day* [day])
+
+* ```day``` - a valid cal-day structure
+
+Configuration parameter specifying the current day. Defaults to
+current date.
 
     (make-cal-period since before [scomment [bcomment]])
 
@@ -222,6 +228,24 @@ Returns ```#t``` if given month ```m``` lies within the period
 Returns ```#t``` if given month ```m``` lies within any of the periods
 given in the list of periods ```ps```.
 
+    (cal-day-in-period? p [d])
+
+* ```p``` - a valid cal-period structure
+* ```d``` - a valid cal-day or cal-month
+
+Checks whether given day ```d``` (or month, after conversion to the
+first day of given month) belongs to period specified by ```p```. The
+period is converted to cal-day period if it is a cal-month period. The
+tested day ```d``` defaults to ```(*current-day*)```.
+
+    (cal-day-in-periods? ps [d])
+
+* ```ps``` - a list of valid cal-period structures
+* ```d``` - a valid cal-day or cal-month
+
+Returns ```#t``` if ```cal-day-in-period?``` returns ```#t``` for at
+least one period in the ```ps``` list.
+
     (cal-periods->string ps)
 
 * ```ps``` - a list of periods
@@ -265,6 +289,14 @@ If ```v``` is a valid month, returns it unchanged. If it is a day,
 uses ```cal-day->month``` for conversion with given ```stop?``` as
 second argument.
 
+    (cal-ensure-day v)
+
+* ```v``` - a valid cal-day or cal-month or ```#f```
+
+Returns a valid cal-day structure based on ```v```. If it is a cal-day
+or ```#f```, returns it unchanged. If it is a cal-month, returns a
+valid cal-day of the first day of given month.
+
 ### Day
 
     (import cal-day)