Index Date Truncation

[ifti_ch2002]

data have;
infile datalines missover; 
   input IDnumber @3 date  mmddyy10.;
   datalines;  
1 4-7-2003 
1 4-7-2009 
1 4-7-2010 
1 4-7-2011 
1 4-7-2012 
1 4-7-2013 
1 4-7-2014 
1 4-7-2015 
1 4-7-2016 
1 4-7-2018 
2 4-7-2005 
2 4-7-2011 
2 4-7-2012 
2 4-7-2013 
2 4-7-2014 
2 4-7-2015 
2 4-7-2016 
2 4-7-2017 
2 4-7-2018 
2 4-7-2019 
2 4-7-2020 
;       
run; 

data want;
infile datalines missover; 
   input IDnumber @3 date  mmddyy10. @12 index_date  mmddyy10.;
   datalines;  
1 4-7-2003  4-7-2003
1 4-7-2009  4-7-2009
1 4-7-2010  4-7-2009
1 4-7-2011  4-7-2009
1 4-7-2012 4-7-2009
1 4-7-2013 4-7-2009
1 4-7-2014 4-7-2014
1 4-7-2015 4-7-2014
1 4-7-2016 4-7-2014
1 4-7-2018 4-7-2014
2 4-7-2005 4-7-2005
2 4-7-2011 4-7-2011
2 4-7-2012 4-7-2011
2 4-7-2013 4-7-2011
2 4-7-2014 4-7-2011
2 4-7-2015 4-7-2011
2 4-7-2016 4-7-2016
2 4-7-2017  4-7-2016
2 4-7-2018  4-7-2016
2 4-7-2019  4-7-2016
2 4-7-2020  4-7-2016
;       
run; 

Hi,

I have data with the different dates by grouping variable "IDnumber". I have calculated index date based on the condition, if first "idnumber" or the difference between current date and lag(date) is greater than 4 years. What i need is to repeat the index date until new index date within the same group. For example the index date on the second line will be repeated untill line number seven.

[PaigeMiller · Accepted solution]

I have calculated index date based on the condition, if first "idnumber" or the difference between current date and lag(date) is greater than 4 years. 

I don't see how the part in red is applied to obtain the desired result.
Why does index date change at 4-7-2014?

[ifti_ch2002]

@PaigeMiller, i accidently accepted the solution. Current date i mean if on the row second then the current date is on the second row. But this is not the question. Question is only to repeat the index date until new index date. Updated question is on the following

https://communities.sas.com/t5/SAS-Programming/Repeat-Index-Date/m-p/647182#M193653