FirstDayOfMonth(date)
Returns the ordinal (the day's number in the year) for the first day of the specified month.
See also Day, DayOfWeek, DayOfWeekAsString, DayOfYear, DaysInMonth, DaysInYear, and FirstDayOfMonth.
Any date.
Years less than 100 are interpreted as 20th century values.
When passing a date/time value as a string, make sure it is enclosed in quotes. Otherwise, it is interpreted as a number representation of a date/time object, returning undesired results.