How to delete old backups on time machine

Nestor Holynskyj wrote:

I'd like to free up space on my Time Machine drive and delete some older backups. I tried doing that directly on the drive (I've since read that's not advisable) but was denied with an error message saying it can't be done because some files are locked. It's not feasible for me to find out which ones they are. Is there an "approved" way of having Time Machine do this properly?

None whatsoever. Do not meddle with Time Machine backups as it consolidates days into weeks, and weeks into months and no one thing can be removed, even if you could.

If you have run out of Time Machine drive space, label the current drive with the operating system, and backup date/time on it, and put it on a shelf. Format a new drive and start a new Time Machine back up to it.

Time Machine will use all the space at its disposal, so probably the only way to reduce its size is to choke it in a smaller space. This means reducing the size of the partition where it resides.

Easier said than done though, because if the partition is fully used the resizer might not know what to throw away.