Every fourth year (i.e. 2016, 2020, 2024) is a Leap Year and the calculation for the Sales Tax Deduction contains a factor in the calculation for the number of days lived in the State. In these years, if you adjust the days entered in this field to "366" (the number of days in a leap-year) as opposed to the usual "365," the sales tax calculation in TaxAct will match the IRS table for the state of residence for full year residency.

In the Q&A, the screen titled Itemized Deductions - Residency Information notes, "The total number or days should not exceed 366."