Calculating average time from military time

I am trying to find the average between a set amount of times, but keep getting an error message (#NAME?) when I type in the formula. I found the duration between two set times in military time. I am trying to find the average of all of the durations calculated. The formula I am using is =AVG() with the cells I want the average from listed in the parenthesis. Can someone please let me know what I am doing wrong? I assume it has something to do with military time. Thank you