DAYNAME Day name function
Description
DAYNAME(date[,languagecode]) returns the name of the day of date. Date can either be a serial date number or a date string.
The optional argument languagecode is a two-character code that defines the language to be used. When omitted, the name of the day is given in English.
Example
When using date format MM.DD.YY:
DAYNAME("12.03.2001") returns "Monday"
DAYNAME("01.30.2012","KO") returns "월요일" (Korean)