Datedif is a simple console program that calculates the difference in days 
between two dates. It has two types of output, the first for scripts and the 
second for shellprompt use. The default output is the script-output, which is 
only the difference in days, not even followed by a carriage return. The second
output can be accessed with the -m option, and it displays an output suitable 
for shellprompt use.