Old TM data to new installed macbook For more than a year my macbook air used a time-machine (local network, synology). After completely new fresh install of my macbook air, i reconnected time machine. In TM, data before the fresh install is not shown if i enter time-machine. Only the backup made after the new install is shown. How can i access the old data? On the TM itself it looks like old and new data is merged.

Kind regards
George
If I recall correctly, Time Machine will notice if there are existing backups on the disk you select and ask if you want to reuse the old backup data.

I haven't tried personally but looks like you can use the tmutil command to inherit a backup, too:

sudo tmutil inheritbackup /path/to/backups


See also:  http://pondini.org/TM/B6.html