If you're talking about the death that the Teselecta predicts at Lake Silencio which turns out to be fake, we saw that happen in "The Impossible Astronaut", and he told us he was 1103 shortly before it happened.
It you're talking about the death that occurs in front of the Teselecta only to be undone by River in "Let's Kill Hitler", we don't know exactly, but 910 seems most likely.
Here's what we know for sure:
He's 909 early in "The Impossible Astronaut".
Between then and the end of "The Almost People", he's either with Amy's ganger or living in real time the entire time. That's over 3 months (because there's 3 months between the first two episodes), no more than 9 months (because Amy's pregnant the entire time). Since Amy went from her first attack of morning sickness to pre-labor pains, it's probably around 7 months.
Between "The Almost People" and "A Good Man Goes to War", he and Rory are going around separately gathering information and allies, which could be any amount of time, but from what we saw it seems plausible that the whole thing took about a week for him.
Between "A Good Man Goes to War" and "Let's Kill Hitler", while Rory and Amy are sitting around at home for 2-1/2 months, the Doctor is off running around time and space trying to track down Melody. We have no idea how long that took him, but based on the way he acts, the gap seems shorter than the one between, say, "A Christmas Carol" and "The Impossible Astronaut", so 2-1/2 months seems reasonable.
So, he's about 10 months older when he gets killed than when he said he was 909, which means he's probably either 910 or close to his 910th birthday.
He could be a bit older than that, but not too much, because it's "almost 200 years" of running between "The God Complex" and "Closing Time", and he's 1103 when he gets shot at Lake Silencio, so he's definitely in his early 900s.