Query: What is a GROUP variable in difference in differences analysis?

Study: Newspaper articles from 1985-2017 were categorized as either in favor, against, or neutral toward a specific topic. These are weighted and graphed.
Hypothesis: An event happened around 2007 that triggered a change in attitudes. I'd like to test this with a DID analysis.
Unit of Analysis: Newspapers for each year.

Outcome Variable: Favor -defined as newspaper articles with a favorable stance
Treatment: Treatment -defined as 0/1 "before 2008" and "2008 and on"
Time Variable: Year -defined as years 1985-2017
Group: ???

Syntax:didregress (Favor) (Treatment), group(?????) time(Year)

DID Model: See the image of the model
Array




A Control Variable?: I don't know if this is needed for DID. I created a dummy variable of the mean of Favor and Against.


Example Data:
Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input int Year byte(Favor Against Neutral Treatment Control)
1985  29 71  0 0 50
1986  16 44 40 0 30
1987  43 43 14 0 43
1988  51 27 22 0 39
1995  60 10 30 0 35
1996  33 57 10 0 45
1997  30 69  1 0 50
1998  50  0 50 0 25
1999  44 31 25 0 38
2000  42 40 18 0 41
2001  80 20  0 0 50
2003  80 20  0 0 50
2004   0 75 25 0 38
2005  38  2 60 0 20
2006 100  0  0 0 50
2007  15 55 30 0 35
2008  19 68 13 1 44
2009  44 38 18 1 41
2010  72 14 14 1 43
2016  88 12  0 1 50
2017  82  9  9 1 46
2018  79  7 14 1 43
end

What is a GROUP variable?