Oracle PL/SQL Date Timestamp Functions :Using Datetime Functions

In the following table, x represents a datetime or a timestamp.

Function	Description
ADD_MONTHS(x, y)	Add y months to x. If y is negative, y months are subtracted from x.
LAST_DAY(x)	Get the last day of the month.
MONTHS_BETWEEN(x, y)	Returns the number of months between x and y. If x appears before y on the calendar, the number returned is positive.
NEXT_DAY(x, day)	Returns the datetime of the next day following x; day is specified as a literal string, for example SATURDAY.
NEW_TIME	Returns the time/day value from a time zone specified by the user.
ROUND(x [, unit])	Rounds x. By default, x is rounded to the beginning of the nearest day. You may supply an optional unit string to indicate the rounding unit.
SYSDATE()	Returns the current datetime set for the operating system.
TRUNC(x [, unit])	Truncates x. By default, x is truncated to the beginning of the day. You may supply an optional unit string that indicates the truncating unit.