dividing time periods into intervals

[lillymaginta]

data test;
input id$2. start  end ;
attrib start format =date9. informat=date9.;
attrib end format =date9. informat=date9.;
datalines;
1 01OCT2014 14JUN2015
1 01OCT2015 14NOV2015
2 18FEB2015 30APR2015;
run;

I have the above data. The max time between the start and the end date is 270 days.

I want to divide the periods into intervals:

period1: 0-90

Period2: 91-180

Period3: 181-270, all would be calculated from the start date.  

Output

id start              end              period 

1 01OCT2014 30DEC2014   1

1 30DEC2014 30MAR2015   2

1 30MAR2015 14JUN2015   3

1 01OCT2015 14NOV2015   1

2 18FEB2015 30APR2015   1

[ballardw · Accepted solution]

This seems to work for the example data:

data test;
input id$2. start  end ;
attrib start format =date9. informat=date9.;
attrib end format =date9. informat=date9.;
datalines;
1 01OCT2014 14JUN2015
1 01OCT2015 14NOV2015
2 18FEB2015 30APR2015
;
run;

data want;
   set test;
   period=0;
   tend = end;
   do start = start to end by 90;
      period= period+1;
      end= intnx('day',start,90);
      if end>tend then end=tend;
      output;
   end;
   drop tend;
run;