Salesforce formulas derive their value from other fields, expressions, or values. They can be used in a number of contexts, including custom fields for auto-calculating values, criteria for data validation and workflow, and Visualforce pages.
Here are the Date Functions available to you whether you are using formula builders in an object or a process or if you are writing the formula in an apex script or visual force page.
|Date and Time Functions|
|DATE||Returns a date value from year, month, and day values you enter. Salesforce displays an error on the detail page if the value of the DATE function in a formula field is an invalid date, such as February 29 in a non-leap year.|
|DATEVALUE||Returns a date value from a date/time or text expression.|
|DAY||Returns the day of the month a given date falls on as a number between 1 and 31.|
|MONTH||Returns the month that a given date falls in as a number between 1 (January) and 12 (December).|
|NOW||Returns a date/time value representing the current moment. TODAY Returns the date value of the current date.|
|YEAR||Returns the year that a given date falls in as a number.|