Cedricgw wrote:
. . .
When i first started my new mac mini (the old one was 4 year old i think), the computer asked (before i finished the set-up, so before i was able to use it) if it should load a previous save done using time machine
i said yes, and it loaded some 70GO of datas more or less
That was the Setup Assistant transferring your stuff, just as it should. That's the best way to set up a new Mac, by far.
the issue i have is that when i open time machine (with finder coming on top and the stars in the background) the right of the screen where i used to see the past dates when time machine had done a previous save are no longer here. therefore, i can not come back a month or a year in the past to find a file i'm looking for, that is my problem
That's correct, at least until you start doing new backups (see below). Those backups are for a different Mac (your old one), and Time Machine normally only shows the backups for the Mac it's running on. You can see and restore from them via the Browse... option, per #E2 in Time Machine - Troubleshooting.
(It's done that way because you can back up more than one Mac to the same place -- many folks back up 2 or 3 to the same Time Capsule.)
When you did the first backup after using Setup Assistant, you should have seen this prompt:
See #B5 in the Troubleshooting article for details.
If you chose Inherit Backup History, new backups would be added to the old Mac's backups, and all appear in the timeline.
If something went wrong and you didn't get the prompt, or if you chose Create New Backup, a whole new set of backups would have been made, separate from the old ones (and you won't see the old ones via Enter Time Machine, only via the Browse option). From your description, that seems to be what happened.
when i go in the external disk dedicated to time machine and i open the folder, there are now 2 different sub folders, which means that time machine knows it is 2 different computers
. . .
i don't know how to make time machine think that i haven't changed computer in the end, that would be more or less the solution i guess
It's not clear why this happened, but you may be able to fix it this way:
The sub-folder for the new Mac should have very little in it; delete it via the Finder and empty the trash.
Then use the procedures in #B6 of the Troubleshooting article to get the new Mac to "inherit" the backups of the old one, and "associate" the new Mac's internal HD with the old backups. It's rather techie, unfortunately, but if you follow the steps and examples carefully, it should work.
One other question: how large is your Time Machine drive? It sounds like it's a bit small. It varies greatly, of course, depending on how you use your Mac, but Time Machine usually needs 2-3 times the space of the data it's backing-up, to be able to keep a reasonable "depth" of old backups for you. You might consider getting a larger drive.s