well, it shouldn't be too difiicult to hide this, but you will need to change it by code.
for example, for the list view:
if you open /components/com_calendarplanner/views/events/tmpl/default.php and go to line 170 approx, you will see that the hour is printed. you would just need to get ride of it.

Thanks. That was really simple for the list view, but it's not that easy for the month view, as it's not acctually just printed out?! Could you tell me, where I can remove it there?

yes, in the month view it's in a different place. where you want to hide it, exactly? when you click on an event? or directly on the little color box shown?

These

the best way to do it in that case is just hide it using CSS.
add this to your template CSS:

.hour_start{
display:none;
}

This works, thank you!