Date Manipulation and Comparision

Hi All,

I want to generate quarter dates using awk or anything, by giving a dates as input
for example :
start_date=2010-01-01
end_date=2010-05-31

output should be:

start_date end_date qtr
2010-01-01 2010-03-31 1
2010-04-01 2010-05-31 2

Example 2:
start_date=2010-01-01
end_date=2010-06-30

output should be:

start_date end_date qtr
2010-01-01 2010-03-31 1
2010-04-01 2010-06-30 2

Thanks in advance...

awk -F \= 'BEGIN{print "start_date end_date qtr"} 
          /start_date/ {print $2,"2010-03-31",NR} 
          /end_date/ {print "2010-04-01",$2,NR}' urfile