Create weekly intervals with different start dates

[VDD]

is this what you are looking for?

data _null_;
	xd = today();
	end=input(put(xd,yymmdd8.),yymmdd8.);
	start='24JAN2019'd;
	call symput('end',put(end,yymmdd10.)); 
	call symput('start',put(start,yymmdd10.));
	put end;
	format start mmddyy10. end mmddyy10. ;
run;
data _null_;
	%put _user_;
run;
data set_weeks;
retain fmtname 'weeks';
start=&start;
end=start+6;
label="Week: "||PUT(start, mmddyy10.)||" - "||PUT(end, mmddyy10.);
OUTPUT;
DO UNTIL (end > &end);
start=start+7;
end=end+7;
label="Week: "||PUT(start, mmddyy10.)||" - "||PUT(end, mmddyy10.);
OUTPUT;
end;
keep fmtname start end label;
format start end mmddyy10.;
run;

[fordcr2]

No, because not all start dates are going to be 24Jan2019. I need the start date to be the date that the participant logged in (participant_startdate).