This article is also available at sportsdata.io.
For NFL, we have a timeframes API that will dynamically return the current & upcoming weeks at any point during the NFL season (including off-season). We also provide static fields, like CurrentSeason and UpcomingWeek to dictate the current point in time of the NFL Season. However, the timeframes endpoint will provide much more meta information than just the current season & week numbers.
Click here to learn more about our NFL Timeframes.