Last season ended in December for us and the Super Bowl is over
This year is 2018
Contracts are generally done in the offseason. We are in the 2018 offseason (i.e. This year's offseason).
My girlfriend has PhD in linguistics so I asked her to review this topic.
She said your statement is not clear. For clarity you should either reference season instead of year or reference the actual year 2018 or 2019.
The fact that you used past tense "I thought" put an emphasis on the past as in this past season vs the upcoming season.
When she saw your statement without any context from me about it, she thought you were likely referring to after the 2017 season.
Sports contracts reference season for clarity.
You were not technically wrong but did not clearly communicate your thoughts.
I was not really wrong but should either have asked which season you were referencing or I could have stated your post was unclear and that Dak can't sign a contract until after his 3rd NFL season which will be in the 2019 offseason.
Bottom Line: Neither of us were wrong but both of us should have worded our post(s) more clearly.