Hello Kurt and thanks for the reply.
Actually, I might have solved the issue in the meantime, although using a different solution than yours. This is what I wrote:
data table_2 (drop=day_p);
set table_1;
day_pp = datepart(input(day_p,yymmddn8.));
run;
data table_3 (rename=day_pp = day_p);
set table_2;
where put(day_pp, yymmddn8.) >= "&MACRODATE";
run;
It seems to be working.