three days from today
Refers to the day three days after today. In some regions or contexts, it can also mean four days from today, but the primary modern meaning is three days from today.
Three days from today is my friend's birthday.
I have to finish this work by three days from today.
four days from today
In some dialects or older usage, やのあさって can mean four days from today. This sense 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, but usage varies by region.
Depending on the region, やのあさって can refer to four days from now.