The board shall, on or before the fifteenth day of January, one thousand nine hundred fifty, and annually thereafter, fix a day as of which the property made taxable by this act shall be listed and returned. The day so fixed shall be between the first and the fifteenth days of the month of January, both inclusive, and the day so fixed shall be printed or stamped on the forms for making returns of all such property. If, through inadvertence, mistake, or otherwise, the board fails to designate or fix such date, or if such date does not appear on the form for making return of such property, the date as of which such property shall be listed and returned shall be the immediately preceding first day of January.
24 P.S. § 581.34