This formula uses 3 different functions:
- IF(logical_test, value_if_true, value_if_false) - Determines if expressions are true or false. Returns a given value if true and another value if false.
- ROUND(number, num_digits) - Returns the nearest number to a number you specify, constraining the new number by a specified number of digits.
- NOW() - Returns a date/time representing the current moment.
Here's a Case view that displays two cases, both open and closed, the fields referenced by the above formula and the formula field itself (# of Days Open).