Syntax:
MONTHNAME(value:(Number|Date)
Returns a text string of the month given by value.
value must be either a number or date value.
If value is a number it is reduced into the range [1,12] (i.e. inclusive).
Examples:
MONTHNAME(27)
returns the text string "March"
MONTHNAME(TODAY)
returns the name of the current month as a text string.