In VBA I know you can use this syntax to subtract a year from a date
Dim testdate As String, DateTest As String
testdate= "03/21/2017"
DateTest = Month(testdate) & "/" & Day(testdate) & "/" & Year(testdate) - 1
But how could you find the first and last date of a given year? For example, let's use the same date
testdate = "03/21/2017"
and get the following values
firstdate = "01/01/2017"
lastdate = "12/31/2017"
If it is always the beginning and the end of the year that interest you, you can just use the 1st of January and the 31st of december. To mimic your syntax :
Dim testdate As String, DateTest As String
testdate= "03/21/2017"
FirstDayOfYear = "1/1/" & Year(testdate)
LastDayOfYear = "12/31/" & Year(testdate)