How to increment a date in a bash script

How to increment a date in a bash script

I have a bash script that takes an argument of a date (yyyy-mm-dd)
I convert it to seconds with
startdate="$(date -d"$1" +%s)";
What I need to do is iterate 8 times, each time incrementing the epoch
date by 1 day and then displaying it in the format mm-dd-yyyy