What does your data look like?
That sort of plot would be done as either a HIGHLOW plot with y= number of subjects and High and Low values the dates indicating the range, or possibly a vector plot in Proc SGPLOT.
Documentation on Sgplot has examples of Highlow plots both horizontal and vertical.
There are a couple of examples at https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/grstatproc/n19gxtzyuf79t3n16g5v26b73ckv.htm#p... that use SAS supplied data sets you should have to test code and work with.