> easy way to do this with httrack? Resulting
> Structure ~/YYMMDDHH/<webstructure> and unchanged
> parts linking to older ~/YYMMddHH/...

No, but if you're using xfs and not FAT/FAT32 you could do it with hardlinks
and a batch file:
if "%~2" == "" (
 echo %0 mirrorDirectory snapshotDirectory&&exit/b
)
setlocal enabledelayedexpansion||pause
for /R %1 %%A in (*) do (
  set origF="%%~A"
  set origD="%%~dpA"
  set newD=!origD:\%~1\=\%~2\!
  set newF=!origF:\%~1\=\%~2\!
  md 2>nul !newF!
  fsutil hardlink create "!newF!" "!origF!"
)