Since we now know G2a3 was present in the LBK of Germany during the neolithic, I decided to run some calculations on G2a3 types using Ken's Generations5 calculator.
The data comes from the FTDna Haplogroup G project.
The following are intraclade ages using mostly G2a3a, G2a3a1, G2a3b, and G2a3b1 as a proxy for a neolithic pattern. Some of the haplotypes were not as fully tested as I would have liked, so that should be taken into account when considering the ages.
G2a3b and G2a3b1(nothing further downstream) - all locations - G=324/17 or 9720+/-510 ybp - n=154
G2a3b and G2a3b1(nothing further downstream) - Europe only - G=313/16 or 9390+/-480 ybp - n=145
G2a3b1+(all downstream) -all locations - G=366/22 or 10980+/-660 ybp - n=220
G2a3b1+(all downstream) -Europe only - G=356/21 or 10680+/-630 ybp - n=207
G2a3a+ - all locations - G=372/20 or 11160+/-600 ybp - n=36
G2a3a+ - Europe only - G=260/18 or 7800+/-540 ybp - n=24
G2a3b1a1a (for comparison) - G=109/12 or 3270+/-360 ybp - n=34
Here's an interclade for G2a3 using G2a3a, G2a3a1, G2a3b and G2a3b1 (nothing further downtstream) - G=529/135 or 15870+/-4050 ybp
As you can see these ages are much older than what we're getting for R1b. G2a3 seems to originate in SW Asia sometime during the upper paleolithic and was probably important to the transition to agriculture there. The Europe only sample for G2a3b and G2a3b1 are in line with a neolithic entry for SE Europe around 7000 BC and the Europe only for G2a3a is very close to LBK in Central Europe. The LBK aDNA was at least G2a3, but I'm not sure exactly what, if any, downstream snp's were tested.