Here is a maintainable version...

DECLARE

@dt datetime,

@DayOneDayOfWeek int,

@DaysInMonth int,

@s-2 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-2 = 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

;