While the oldest living trees are there, its not living trees that are being dated. If you find a timber used in the construction of the pyramid, you can then match its tree rings up with another set of tree rings that overlap, and so on back to the present age. In theory.

See https://www.crowcanyon.org/index.php/dendrochronology

The challenge is there are gaps and spots where it doesn't quite match up. A bad few years and it throws the tree rings off. However, if you can pinpoint some reference event that spans the globe, you can line the samples back up again. This is known as cross dating ( http://www.ltrr.arizona.edu/lorim/basic.html ) - it doesn't need to have a living tree.

Radiocarbon dating will never be precise (being able to pin down a specific year) because of the probabilistic nature of decay and the errors on that are on the sample. Carbon dating only gives a one sigma. Something that is 3500 BP (before present) can have a +/- 60 year error on it. Give https://en.wikipedia.org/wiki/Calculation_of_radiocarbon_dat... a read.