How to build interactive calendar

Hi, I’m struggling here with how to build an interactive calendar. Basically, for a one month span, I want to be able to add colored lines on each day a particular project is active. I need to figure out how to get the lines to go over the columns when they will all be different lengths. I considered using a 7 day row, then another row below it and then setting spacer images widths based on the number of days a job is active.

I’m not sure if that will work. Does anyone have any bright ideas?