When Congress did the Amnesty of 1986, they set the date Jan 1, 1972. And the language they describe to qualify are as follows.

In order to qualify, an applicant must have been in the United States Unlawfully anytime since before the cut off date ( Jan 1, 1972)

A person is also qualified for registry and is returning from a short trip abroad should also be able to seek registry in the event she/he is placed in proceeding upon return.

In your case, maybe 2-3 weeks is a short trip, I guess.