In Excel, you can use the EOMONTH() function to return the first or last day of a month.
Syntax
EOMONTH(start_date, months)
The EOMONTH function syntax has the following arguments:
Start_date
- Required. A date that represents the starting date. Dates should be entered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2015,7,23) for the 23rd day of July, 2015. Problems can occur if dates are entered as text.
Months
- Required. The number of months before or after start_date. A positive value for months yields a future date; a negative value yields a past date.
NOTE If months is not an integer, it is truncated.
Examples
To return the LAST day of the current month:
=EOMONTH(TODAY(),0)
The 0 in the second parameter denotes the current month.
To return the FIRST day of the current month:
=EOMONTH(TODAY(),-1)+1
This means, return the last day of the previous month PLUS one day (i.e. the first day of the current month).
By the same token, to return the FIRST day of the next month:
=EOMONTH(TODAY(),0)+1
The result will be a serial number. To convert this to a displayable string:
=TEXT(EOMONTH(TODAY(),1), "MM/DD/YYYY")
