I have always been struck by his 'inserting most accurately the day of the month on which he had lost his wife.'

Is this simply his obsessiveness about the details of his own life... or could it reflect some genuine feeling on his part? JA uses the phrase 'he had lost his wife, not his wife had died - the emphasis is on his loss. I like to think that there was some genuine affection, or at least some appreciation of what she did for him, on his part, which prompted that annotation.