:- module calendar.
:- interface.
:- import_module io.
:- type date.
:- type day_of_month == int.
:- type day_of_week
	--->	monday 
	;	tuesday 
	;	wednesday 
	;	thursday 
	;	friday 
	;	saturday 
	;	sunday .
:- type days == int.
:- type duration.
:- type hour == int.
:- type hours == int.
:- type microsecond == int.
:- type microseconds == int.
:- type minute == int.
:- type minutes == int.
:- type month
	--->	january 
	;	february 
	;	march 
	;	april 
	;	may 
	;	june 
	;	july 
	;	august 
	;	september 
	;	october 
	;	november 
	;	december .
:- type months == int.
:- type second == int.
:- type seconds == int.
:- type year == int.
:- type years == int.
