Math Expression in Views: Date functions like now() Is there Date expressions or function? I'd like to calculate a duration between a date field and today ? Is there a now(), today() function?
i'd like this kind of math expression: now() - [field_arrival]
If you only want to display the duration between the given date and today in a view then you don't need any calculation.

Just use time ago display option and display your given date with this time ago option. 

You will have the result something like this -- 1 year 3 months ago. 

You can drop text ago if you don't need.