Currently, I'm using your Calendar component for a vacation request feature. It works decently for picking dates in that I can use CTRL and Shift to select many dates. I'm currently making the page responsive but the mobile user experience lacks because there is no way to select more than one date.

The ideal user experience would be to be able to single click (or tap from mobile) to select a date and be able to do that on as many dates as preferred (to select many). Clicking/tapping again would deselect the date. That would be better in both the desktop and mobile versions and more intuitive for a user (as no one has initially assumed CTRL and Shift work - I have had to train them).