跨多个目录同步文件修改时间

I have a computer A with two directory trees. The first directory contains the original mod dates that span back several years. The second directory is a copy of the first with a few additional files. There is a second computer be which contains a directory tree which is the same as the second directory on computer A (new mod times and additional files). How update the files in the two newer directories on both machines so that the mod times on the files are the same as the original? Note that these directory trees are in the order of 10s of gigabytes so the solution would have to include some method of sending only the date information to the second computer.I have a computer A with two directory trees. T