Is fasting the last day of the the Hijri year, with the intention of ending the year with a good deed from which expiation of sins is hoped for, considered an innovation (bid'ah)?

Designating this day for fasting and believing in its virtue is an innovation (bid‘ah), unless it coincides with a person’s usual fasting habits. The best guidance is the guidance of Muhammad, peace and blessings be upon him. The Messenger, peace and blessings be upon him, legislated specific days for fasting. One may fast whenever it is easy, without believing in a specific matter, but rather for the virtue of fasting and with the intention of gaining its reward.