intnx function with a interval name adding shift-index

[Steve1964]

Run DATA step in the following

DATA _null_;
x1=intnx('week','5APR2020'd,0);
x2=intnx('week','5APR2020'd,1);
y1=intnx('week.2','5APR2020'd,0);
y2=intnx('week.2','5APR2020'd,1);
put (x1 x2 y1 y2) (yymmdd10.);
run;

output reads
2020-04-05 2020-04-12 2020-03-30 2020-04-06


I can't understand why intnx('week.2','5APR2020'd,0) return to 2020-03-30,but intnx('week','5APR2020'd,0) to 2020-04-05,since increments are 0. in the both functions.

[PaigeMiller · Accepted solution]

intnx('week.2','5APR2020'd,0)

finds the first day of the week (where week is defined as starting on a Monday) of the week of April 5, 2020, which is March 30, 2020.

intnx('week','5APR2020'd,0)

finds the first day of the week (where week is defined as starting on a Sunday) of the week of April 5, 2020, which is April 5, 2020.