Urgently need to delete old backups from Time Machine.

Jon H. wrote:

Time Machine not deleting old backups: I was previously backing up an external hard drive which I have now disconnected and no longer want to back up. I have excluded the old HD from time machine backups. My backup drive is full, and is giving the full disk error message.

I keep reading that "time machine manages itself", but this is not the case. (Should note: looking around, lots of people are sharing this complaint.) I see that this current iteration of Time Machine no longer allows deleting old backups, but this is exactly what I need to do.

So now my time machine backups are frozen in time, and I really need to back up my computer particularly because I no longer am using that old hard drive.

To reiterate: I need to do a backup now. If time machine will eventually clear the old data, great, but that does not solve my problem. So what do I do? Just wipe out my backup drive and start fresh? This seems like a bad idea.

It is not recommended to manually delete backups — you will corrupt the complex TM database.

Your best bet is to reformat the drive and start a new backup.

Erase and reformat a storage device in Disk Utility on Mac

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

If you value your user data

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

More than one device, more than one backup methodology— and backup regularly.

—Back up your Mac Back up your Mac with Time Machine - Apple Support

Time Machine is willing to connect one (or more) additional backup drives and begin a new backup staring at this moment. When both are still connected, backups written to the drives are alternated -- every-other backup goes to every-other drive.

Each backup drive is independent, and any can be removed (or erased to start over) whenever you like.

As John Galt suggests, buy a bigger drive and start a new backup now. After next week, it will be up-to-date enough and you can re-arrange.

If I understand the question, your exigent need is to create a backup. If that is correct you do not need to erase the existing backup drive; you need to obtain a new one. Do that.

Time Machine will absolutely, positively erase old and "expired" backups on its own. There are several reasons that TM may not appear to do that, including the presence of TM backups for another Mac on that same backup drive. That "other Mac" may in fact be the exact same one, except its source drive may have been renamed. If that occurs, Time Machine will consider its backups separate and distinct from any other. They will forever be locked in place and unalterable, awaiting return of that "other" Mac. If coping with the resulting significantly reduced capacity is not an option then the only remedy that is to erase the backup drive.

Other reasons include the apparently irresistible temptation to open the backup drive with the Finder and manipulate its contents. Fortunately that is no longer possible, but it had been in the past, and the effect was to permanently and irrevocably corrupt the backup, rendering it useless.

Another popular cause is the use of non-Apple "anti-virus" and / or "cleaning" junk inflicted on the TM backup drive. Those products remain disturbingly commonplace even to this day. The effect on TM is the same: corruption.

All anyone needs to do with Time Machine is

1. turn it on
2. forget about it

Users who do that don't come here to complain, because it works. Users who fail to follow those two simple steps foment falsehoods, misleading, and damaging information instead.