Internet Explorer

DoneCal is built specifically to use the latest web techniques and some of these are not supported on Internet Explorer. Especially older versions that are sadly still quite popular.

Nothing is done deliberately to make it not work in Internet Explorer but there are no intentions to fix potential problems in DoneCal just to make it work with Internet Explorer's idiosyncrasies.

If you are unfortunate enough to be stuck with an old version of Internet Explorer your options are either to upgrade to the latest version or, better, change to a free and secure browser such as Google Chrome or Mozilla Firefox.