Today is Saturday, March 10, 2018. It is the waning days of the 2017 league year when it comes to the NFL. The new league year officially begins on Wednesday, March 14. And yet there have already been 10 trades agreed upon prior to then, including four made just yesterday, and many of them very significant.
None of them have technically as yet happened. Notice that I specifically said that they have been agreed upon, and avoided saying that they have been made, because they have not. Technically, something can fall through with any of these trades that will wipe them out, and one trade could have a ripple effect on others.