To further complicate matters, The Times has a habit of hanging on to obituaries until they have a linked group. So one day they might carry all miltary folk, another day scientists & engineers. I've noted when this happens that an obituary may be up to a couple of months old. But if the person concerned is reasonably well known to the general public, then I believe there is little delay. And maybe, to define "reasonably well known", that's when the death of the individual concerned is reported on the news pages.