diff --git a/lib/modules/Calendar.pmod/module.pmod b/lib/modules/Calendar.pmod/module.pmod
new file mode 100644
index 0000000000000000000000000000000000000000..2b2fada6921170c215bc2ec424e8b4599c0e0a8b
--- /dev/null
+++ b/lib/modules/Calendar.pmod/module.pmod
@@ -0,0 +1,116 @@
+
+//! module Calendar
+//!    
+//!   This module implements calendar calculations, and base classes
+//!   for time units. 
+//!
+//!   example program:
+//!   <pre>
+//!	void write_month(object m)
+//!	{
+//!	   object w;
+//!	   object today;
+//!	
+//!	   today=function_object(object_program(m))->Day();
+//!	
+//!	   write(sprintf("    %|28s\n",
+//!			 Simulate.capitalize(m->name()+" ")
+//!                      +m->year()->name()));
+//!	   
+//!	   w=m->day(1)->week();
+//!	
+//!	   write("    ");
+//!	   foreach (Array.map(w->days(),w->day)->week_day_name(),string n)
+//!	      write(sprintf("%3s ",n[0..2]));
+//!	   write("\n");
+//!	
+//!	   do
+//!	   {
+//!	      array a;
+//!	      object d;
+//!	      a=Array.map(Array.map(w->days(),w->day),
+//!			  lambda(object d,object m) 
+//!			  { if (d->month()!=m) return 0; else return d; },m);
+//!	
+//!	      write(sprintf("%3s ",w->name()));
+//!	      foreach (a,d)
+//!		 if (d)
+//!		    if (d!=today) write(sprintf(" %2d ",d->month_day()));
+//!		    else write(sprintf(">%2d<",d->month_day()));
+//!		 else write("    ");
+//!	
+//!	      write("\n");
+//!	      w++;
+//!	   }
+//!	   while (w->day(0)->month()==m);
+//!	}
+//!    </pre>
+//!	call with, for example, 
+//!	<tt>write_month(Calendar.Swedish.Month());</tt>.
+//!
+//! class time_unit
+//!
+//! method array(string) lesser()
+//!	Gives a list of methods to get lesser (shorter) time units.
+//!	ie, for a month, this gives back <tt>({"day"})</tt>
+//!	and the method <tt>day(mixed n)</tt> gives back that 
+//!	day object. The method <tt>days()</tt> gives back a
+//!	list of possible argument values to the method <tt>day</tt>.
+//!	Concurrently, <tt>Array.map(o->days(),o->day)</tt> gives
+//!	a list of day objects in the object <tt>o</tt>.
+//!
+//!	
+//!	Ie:<pre>
+//!	array(string) lesser()    - gives back a list of possible xxx's.
+//!	object xxxs()     	  - gives back a list of possible n's.
+//!	object xxx(mixed n)       - gives back xxx n
+//!	object xxx(object(Xxx) o) - gives back the corresponing xxx 
+//!	</pre>
+//!
+//!	The list of n's (as returned from xxxs) are always in order.
+//!
+//!	There are two n's with special meaning, 0 and -1.
+//!	0 always gives the first xxx, equal to 
+//!	my_obj->xxx(my_obj->xxxs()[0]), and -1 gives the last,
+//!	equal to my_obj->xxx(my_obj->xxxs()[-1]).
+//!
+//!	To get all xxxs in the object, do something like
+//!	<tt>Array.map(my_obj->xxxs(),my_obj->xxx)</tt>.
+//!
+//!	xxx(object) may return zero, if there was no correspondning xxx.
+//!
+//! method array(string) greater()
+//!	Gives a list of methods to get greater (longer) time units 
+//!	from this object. For a month, this gives back <tt>({"year"})</tt>,
+//!	thus the method <tt>month->year()</tt> gives the year object.
+//!
+//! method object next()
+//! method object prev()
+//! method object `+(int n)
+//! method object `-(int n)
+//! method object `-(object x)
+//!	next and prev gives the logical next and previous object.
+//!	The <tt>+</tt> operator gives that logical relative object,
+//!	ie <tt>my_day+14</tt> gives 14 days ahead.
+//!     <tt>-</tt> works the same way, but can also take an object
+//!	of the same type and give the difference as an integer.
+
+#define error(X) throw(({(X),backtrace()}))
+
+class _TimeUnit
+{
+   object this=this_object();
+
+   array(string) greater() { return ({}); }
+   array(string) lesser() { return ({}); }
+
+   int `<(object x) { error("'< undefined\n"); }
+   int `>(object x) { error("'> undefined\n"); }
+   int `==(object x) { error("'== undefined\n"); }
+
+   object `+(int n) { error("`+ undefined\n"); }
+   object|int `-(int n) { error("`- undefined\n"); }
+
+   object next() { return this+1; }
+   object prev() { return this+(-1); }
+}