Can DNA reveal your age?

yes.
dna has telomeres, that shorten as time passes. one can make conclusion regarding your age by examining these telomeres.

Probably not precisely. Chromosomal DNA is a very long molecule that is constantly undergoing mutations. However, the ends of chromosomes, the so-called telomeres do get shorter over time. So, theoretically you could tell by looking at telomere length (at best a rough estimate), but since everyone starts with a unique length to begin their life, there is no way to determine a precise age with a “snapshot” how much shorter the telomere is relative to the initial one.

In theory (but not in practice), if you had DNA from birth, and then collected DNA at intervals over a lifetime, you might be able to predict age (relatively speaking), but the shortening of the telomeres is also not a finite or predictable event, and as such you would only be able to generate a very rough estimate. This would also depend on the which cell type you used to measure the telomeres, as this too varies within an individual.

Would the DNA in stem cells have original length telomeres? If so, you could compare that to current telomere length. If you had correlation matrix relating stem cell length to telomere length (assuming they differ), you might be able to get an approximation of age. I have no idea how accurate you could make that approximation.

@daloon
you could apply an average annual shorting based on statistics involving a sizeable amount of human test subjects, of which you know the age.
the result would only be an approximation, though.

also iirc, neurons have the lowest mitosis rate and therefore the least telomere shorting and are thus closest to the original length. or sperm/egg cells

There is an excellent group of websites on DNA which could help with your DNA questions
http://www.dnalc.org/ddnalc/websites/ The answer we got for this in Forensics was with a fairly decent realm of possibility yes but absolutely no..Hope This Helps
Amy Price PhD