is mon->subtract_businessdays(days => 5)->day_of_week, 1, "mon - 5 => mon";
is mon->subtract_businessdays(days => 12)->day_of_week, 4, "mon - 12 => thu";
is mon->subtract_businessdays(days => 5)->day_of_week, 1, "mon - 5 => mon";
is mon->subtract_businessdays(days => 12)->day_of_week, 4, "mon - 12 => thu";