Hi, I have data on b1 (month of birth) and b2 (year of birth). I want to go back 9 (nine) months from the date of Birth. Like for the first observation ( 7, 2014), I want to have in row (6,2014) , (5,2014), (4,2014), (3,2014), (2.2014), (1,2014) , (12,2013) ,(11,2013)...

How I can do this, please.

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Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input byte b1 int b2
 7 2014
10 2008
11 2006
 9 2004
 6 2002
 7 2012
 4 2010
10 2004
 9 2002
 5 2000
12 2011
 5 2009
 6 2008
10 2005
 9 2001
 1 2011
12 2006
 9 2003
 7 1999
11 2013
 5 2017
 8 2015
 1 2014
 6 2011
 8 2006
11 2009
 9 2005
 7 2003
 4 1999
12 1997
11 2015
 1 2012
 4 2015
 3 2013
 7 2007
12 2005
 4 2003
 6 2001
 3 2016
 8 2013
 9 2005
12 2004
 2 2003
 4 2001
 5 2010
 6 2009
 8 2004
 4 2000
 6 1998
11 2014
 3 2012
 7 2009
12 2007
 8 2005
 5 2001
 5 2014
 6 2011
12 2004
 7 2002
 6 2000
 3 2017
 6 2014
 5 2011
 4 2007
10 2005
12 1997
 7 2014
 9 2009
 8 2005
 5 2004
 6 2002
 3 2015
 7 2005
12 2002
 9 2001
 6 2000
11 1990
10 2016
 7 2017
 4 2010
 8 2005
 9 2017
 6 2012
 7 2017
 6 2015
 4 2011
 4 2009
10 2016
 5 2014
 2 2008
 7 2005
 6 2003
 9 2011
 4 2005
11 2002
 8 2000
 3 2005
 5 2000
 2 1997
 6 2017
end