How to Find First and Last Day of a month with EOMONTH function

      To solve this problem in old days, we had to use DATEADD function to calculate first or last day of a month. SQL Server 2012 has a built-in function named EOMONTH to handle this for you.

EOMONTH(inputdate [,month_to_add])

Let's try to find the last day of January 2017 by using EOMONTH function

Function will add/subtract month_to_add option to inputdate if it's available.

To find a first day of a month, we need use DATEADD function with EOMONTH function.

Here is the first and the last day of January 2017