I am trying to figure out the duration between one day's survey begin time (e.g., 7:13:45) and end time (e.g., 9:39:53) in an attribute table of a line shape file. It has just two attributes begin and end. But $lengh returns an error message and cannot figure out the duration. I suspect that the fields are not in proper format. So, I try to update the fields with
Then, it says Eval Error: Cannot convert '7:13:45' to Time.
What is a remedy? The “begin” and “end” are in string.