Gifted $100,000 in 2017 by father but he was not required to file tax return for same year & did not file 709 Gift Tax form can that be filed for 2018 without penalty?

I was gifted $100,000 in 2017 from my father. We were told due to his lack of income (only social security) he was not required to file. The Gift Tax form (709) was not filed. Should the form be filed in 2018 by 04/15/2019 and are there repercussions by not filing on time?