The time studied is shown in days, not hours.
5.6 centidays

This add-on is just me riding my favorite hobby horse, metric time. I think splitting days into hours, minutes and seconds is about as silly as splitting lengths into inches, feet, yards, rods, chains and miles or using pounds and ounces and stones and who-knows-what else for mass. (Or weight. Better not go there! And how much is a gallon‽)

This add-on needs extra Python packages. See the Batteries page for details.

This add-on replaces the standard time-formatting function with one that returns times shorter than a year as days – even times much shorter than a day. Longer times are written as years with one decimal place.

This is an Anki 2.0 plugin. I have no plans of updating it. People that are interrested in this are welcome to take this over.

AnkiDroid

Daring spirits can use my branch of AnkiDroid development branch.

I have added the equivalent of this add-on, showing times as fractional days in AnkiDroid. You should merge this branch into the newest version of AnkiDroid, not just use that branch as-is. I forked this off the the 2.1 branch. Merging it into the 2.0 branch may or may not work.