It should be noted that it is only suspected that the Equation Group is related to the NSA. I only bring this up not because I don't think it is but rather to emphasize that it has not been proven yet.
If nothing else, I found this compelling*
> In addition, timestamps in the malware seem to indicate that the programmers worked overwhelmingly Monday–Friday in what would correspond to a 08:00–17:00 workday in an Eastern United States timezone.
*assuming you trust the timestamps.