How to solve Thunderbird Lightning calendar appointments showing as overlapping

Have you added a 15min appointment next to another one and see those as overlaping appointments on Thunderbird Ligntning calendar? Something like this:

This has been something I could not fix for quite a while until I finally found this article answered by user called "Decathlon" (THANK YOU Decathlon!)

In summary, if you play with zooming factor (CTRL +/-) you may be able to correct that but it had to do with font size, height of events, number of hours displayed etc. That article suggests the following: 

To avoid the problem you have to increase the zoom factor, or you can add some css code in the userChrome.css file in order to reduce the minimum height of the boxes. Without changing the font size, you can try something like:

.calendar-event-box-container {
    margin: 0px !important;
}

but obviously the problem arises again if the zoom factor is too little.

I decided just to change zoom with CTRL + and got this: