Inception

[blackmage_nuke]

As I said its hard to gauge how much time passed since he left, assuming it was a year is as much an assumtion as assuming it were a month. The strange lighting might represent how he was dazed and the reality became 'dreamlike'. Have you ever had that moment when you are with someone and it feels like you're the only people in the world?

edit: ^Ive been looking for that exact phone conversation because thats what I felt would be the best indicator but Ive only found vague summaries

Not to even mention how quickly and cleanly everything wrapped up in the end. It was like he woke up and everyone's there and he's home a minute later. It was just such a sped up, neat and tidy happy ending that it all seems more like a dream than an ending that actually takes place in the real world.

You might not have noticed but it actually does that through the entire movie EXCEPT when theyre in the dream world. Cobb travels from place to place with seemless time breaks, things happen one after the other very quickly and cleanly.
Example:
He needs a new architect
he imediately appears at a university to talks to his father in law, he mentions an architect he knows
Ariadne appears litterally (i think) in the next shot they are suddenly in the coriddor
All of the sudden theyre on the roof

Later they have a training montage.

The fact that it wraps up cleanly is just as much an arguement that its reality as much as it is an arguement that the whole movie is a dream!

And as you said the neat tidy happy ending that seems like a dream, maybe its telling us that dreams can come true.