When January 1 is on a Saturday (as it is in 2022), the United States calendar for the prior year (in this case 2021) has holiday New Years Day (Observed) on December 31 even when shift_exceptions contains an exception for January 1.

work holiday: 2021-12-31 [fri] - New Years Day (Observed)

shift_exceptions = ((1, 1),
                    (12, 25),
                    )