also: やなさって
three days from today
Refers to the day three days after today. In some regions, this may be understood as four days from today, so context or clarification may be needed.
See also: やのあさって
I plan to go see a movie with a friend three days from today.
four days from today
In some dialects or older usage, やなあさって can mean four days from today. This meaning is less common and may cause confusion; many speakers use しあさって for 'three days from today' and やのあさって for 'four days from today'.
See also: やのあさって
Depending on the region, やなあさって can refer to four days from now.