There are a few different ways that you can calculate the first business day of the month in Excel. One way is to use the EOMONTH function. This function returns the last day of the month, which is also the first business day of the next month. You can use this function by entering the following formula into a cell:

=EOMONTH(A1,0)+1

Where A1 is the cell containing the date you want to find the first business day of the month for. You can also use the WORKDAY function to calculate the first business day of the month. This function takes into account holidays and weekends, so it is a more accurate way to calculate the first business day of the month. The formula for this function is:

=WORKDAY(EOMONTH(A1,0),1)

You can also use a combination of the DATE, DAY, and WEEKDAY functions to calculate the first business day of the month. The DATE function returns a date given a year, month, and day. The DAY function returns the day of the month for a given date. The WEEKDAY function returns a number from 1-7 that corresponds to a day of the week (1 is Sunday, 2 is Monday, etc.). Using these functions, you can create a formula that will return the first business day of any given month by entering the following into a cell:

=DATE(YEAR(A1),MONTH(A1),1+8-WEEKDAY(DATE(YEAR(A1),MONTH(A1),1)))