On a month view, for an event, only the Start time is displayed (mouse pointer on the event will display a pop up with all the information... but event need to be pointed).
I submit a request feature to have both Start and End time of an event in month view.
This feature is allowed in Outlook, and also in EssentialPIM (selection box : Show for appointments Start & End times).
There is a hack for Thunderbird wich modifies few lines in calendar-month-view.js and permit this feature, so may be it can be included for a next release.
See picture join for the result