DATE
DATE(year, month, day)
year- The year component of the date.month- The month component of the date.day- The day component of the date.
DATEVALUE(date_string)
date_string- The string representing the date.
DAY(date)
date- The date from which to extract the day. Must be a reference to a cell containing a date, a function returning a date type, or a number.
DAYS(end_date, start_date)
date- The date from which to extract the day. Must be a reference to a cell containing a date, a function returning a date type, or a number.