Perhaps something like this:
declare @s char(5)
set @s = '01Q13'
select dateadd(year, convert(int, right(@s, 2)), startDt) as startDt
,dateadd(year, convert(int, right(@s, 2)), endDt) as endDt
from (
select '01', convert(datetime, '2000-01-01'), convert(datetime, '2000-03-31') union all
select '02', convert(datetime, '2000-04-01'), convert(datetime, '2000-06-30') union all
select '03', convert(datetime, '2000-07-01'), convert(datetime, '2000-09-30') union all
select '04', convert(datetime, '2000-10-01'), convert(datetime, '2000-12-31')
) d ([Q], [startDt], [endDt])
where Q = left(@s, 2)
OUTPUT:
startDt endDt
----------------------- -----------------------
2013-01-01 00:00:00.000 2013-03-31 00:00:00.000
Be One with the Optimizer
TG