DECLARE
	@dt datetime,
	@DayOneDayOfWeek int,
	@DaysInMonth int,
	@s varchar(200),
	@crlf varchar(2)
;

SET @dt = '20130401';
SET @crlf = char(13) + char(10);

-- get max days in month: calculate first day of the next month and subtract one day
SET @DaysInMonth = (select datepart(day, dateadd(day, -1, dateadd(month, 1, cast(convert(varchar(8), @dt, 121)+'01' as datetime)))));

-- need to know day one weekday
SET @DayOneDayOfWeek = (select DatePart(WeekDay, cast(convert(varchar(8), @dt, 121)+'01' as datetime)));

-- build day numbers string and pad for first day
SET @s = REPLACE(SUBSTRING(' <<  January YEAR  >> << February YEAR  >> <<   March YEAR   >> <<   April YEAR   >> <<    May YEAR    >> <<   June YEAR    >> <<   July YEAR    >> <<  August YEAR   >> << September YEAR >> <<  October YEAR  >> << November YEAR  >> << December YEAR  >>', (DatePart(month, @dt) - 1) * 21 + 1, 21), 'YEAR', cast(DatePart(year, @dt) as varchar(4)))
	+ ' Su Mo Tu We Th Fr Sa' 
	+ replicate('   ', @DayOneDayOfWeek - 1)
	+ left('  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31', @DaysInMonth * 3)
;

-- Format for display by removing leading space and adding CRLF for each line.
print 
	SUBSTRING(@s, 2, 20)
	+ @crlf + SUBSTRING(@s, 23, 20)
	+ @crlf + SUBSTRING(@s, 44, 20)
	+ @crlf + SUBSTRING(@s, 65, 20)
	+ @crlf + SUBSTRING(@s, 86, 20)
	+ @crlf + SUBSTRING(@s, 107, 20)
	+ @crlf + SUBSTRING(@s, 128, 20)
	+ case when len(@s) > 149 then @crlf + SUBSTRING(@s, 149, 20) else '' end
;