first day of duty was 12/28/2020
The final military pay for tax year 2020 was posted on Wed, Dec 30 for most, Dec 31 for others. If 12/28/2020 was your first day of basic training, then I doubt you got a DFAS issued W-2 for 2020. But it's possible you did if you were paid some cash up front by the military, which is what they usually do your first "official" day of training. The day you arrive at basic training is not your first official day.
