Hello websource,
Our calendar uses the time format that you set in the General WordPress Settings. To change the time to 24 hours format (like 21:00-23:00) go to Settings –> General in your WordPress dashboard. Scroll down to the Time Format and you’ll see several options, including one for 24 hour time.
This time format will show in most of the calendar, but do keep in mind that there are a few places where the time is hard coded so it always appears in the US style. We are working on improving the international compatibility of the plugin.
Best,
Leah