What's the difference?
I was at home all day
and
I've been at home all day
Google translate doesn't see the difference.
The first uses the past tense, the second is perfect. You might want to look at the "usual" differences between the past and perfect.
You might say "I was at home all day last Wednesday" (talking about a time in the past). You couldn't use the perfect in that context.
But if you mean "I (was/have been) at home until now" it would be natural to make the connection to the present by using the present perfect "have been".