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Returns the day of the week for the given date value. The day is returned as an integer between 1 (Sunday) and 7 (Saturday) if no type or type=1 is specified. For other types, see the table below.
WEEKDAY(Number [; Type])
Number, as a date value, is a decimal for which the weekday is to be returned.
Type is optional and determines the type of calculation.
| Type | Weekday number returned | 
|---|---|
| 1 or omitted | 1 (Sunday) through 7 (Saturday). For compatibility with Microsoft Excel. | 
| 2 | 1 (Monday) through 7 (Sunday). | 
| 3 | 0 (Monday) through 6 (Sunday) | 
| 11 | 1 (Monday) through 7 (Sunday). | 
| 12 | 1 (Tuesday) through 7 (Monday). | 
| 13 | 1 (Wednesday) through 7 (Tuesday). | 
| 14 | 1 (Thursday) through 7 (Wednesday). | 
| 15 | 1 (Friday) through 7 (Thursday). | 
| 16 | 1 (Saturday) through 7 (Friday). | 
| 17 | 1 (Sunday) through 7 (Saturday). | 
These values apply only to the standard date format that you select under .
=WEEKDAY("2000-06-14") returns 4 (the Type parameter is missing, therefore the standard count is used. The standard count starts with Sunday as day number 1. June 14, 2000 was a Wednesday and therefore day number 4).
=WEEKDAY("1996-07-24";2) returns 3 (the Type parameter is 2, therefore Monday is day number 1. July 24, 1996 was a Wednesday and therefore day number 3).
=WEEKDAY("1996-07-24";1) returns 4 (the Type parameter is 1, therefore Sunday is day number 1. July 24, 1996 was a Wednesday and therefore day number 4).
=WEEKDAY("2017-05-02";14) returns 6 (the Type parameter is 14, therefore Thursday is day number 1. May 2, 2017 was a Tuesday and therefore day number 6)
=WEEKDAY(NOW()) returns the number of the current day.
To obtain a function indicating whether a day in A1 is a business day, use the IF and WEEKDAY functions as follows: 
IF(WEEKDAY(A1;2)<6;"Business day";"Weekend")