fiveWeekends()={
	my(day=6);	\\ 0 = Friday; this represents Thursday for March 1, 1900.
	my(ny=[31,30,31,30,31,31,30,31,30,31,31,28],ly=ny,v,s);
	ly[12]=29;
	for(year=1900,2100,
		v=if((year+1)%4,ny,ly);	\\ Works for 1600 to 2398
		for(month=1,12,
			if(v[month] == 31 && !day,
				if(month<11,
					print(year" "month+2)
				,
					print(year+1" 1")
				);
				s++
			);
			day = (day + v[month])%7
		)
	);
	s
};