The NOW function returns the current date in minutes. It's used to compare dates from different report fields or columns with the current time.
A report displays the number of days left until a task is done:
Note: the difference between the task's planned completion date (column C) and the value returned by the NOW function is calculated in minutes. Therefore, if you want to display the result in days, divide the value you get by 1440 (the number on minutes in a day).