getting message "Not a valid month" on calendar extension

[#1]

I have installed and configured the Event Calendar extension.   I can get this to work on the current month only. if I choose a past month I get the message 'Not a valid Month'.   What am I doing wrong????  There are events for the past month.  The calendar show the event just not a calendar or the events in the calendar.

[Gysbert_Wassenaar]

Perhaps the date format is wrong. 23 is a valid number for a day, but not for a month. So 23/01/2016 is DD/MM/YYYY, but perhaps the extension expects a MM/DD/YYYY date.

[#3]

Thank you for your reply.  The calendar does work for the Current month of May, not just other months. 

[#4 · Accepted solution]

I figured out my issue.  In order for the Extension Calendar to work, the Month name must be in three letters only. Once I did this I can select any month and the Calendar for that month will appear.