"The whole meal is delicious."
Translation:Ολόκληρο το γεύμα είναι νόστιμο.
Truth is, ο ολόκληρος χρόνος can be said on its own, but has no "real" meaning. It's like saying "the whole cake" without a "time" meaning but as a characteristic of the year (ie that it is whole, as if a year could be cut!). Only just demonstratively. An example is saying "the whole year is better than the half year" Ο ολόκληρος χρόνος είναι καλύτερος από τον μισό χρόνο.But you can't say "i did piano lessons the whole year" using ο ολόκληρος χρόνος. You have to say έκανα μαθήματα πιάνου ολόκληρο τον χρόνο. Ie in any other context where you want to say "the whole" year (using the phrases "time" meaning) you would have to say ολόκληρος ο χρόνος. But since the sentence with ο ολόκληρος χρόνος causes trouble, we'll see to it...
I came up with a better example on when to use for example "το ολόκληρο κέικ" or "ολόκληρο το κέικ". Θέλω να φάω ολόκληρο το κέικ=I want to eat the whole cake. Θέλω να φάω το ολόκληρο κέικ=I want to eat the cake that is whole (ie no one else has gotten a bite yet and the cake is whole, but that does not mean I want to eat it all). So saying "ο ολόκληρος χρόνος" is like saying "the year that is whole (which has no real meaning because years can't be cut), but "I've been doing it the whole year=Το έκανα ολόκληρο τον χρόνο."
If i understand right, the subject of the sentence is ολόκληρο and the object (acc.?) is το γεύμα, το κέικ, τον χρόνο.
The subject of Duo's sentence is ολόκληρο το γεύμα.
όλοκληρο τον χρόνο is not a subject or an object but rather an expression of time (acting as an adverbial).