The canonical answer seems to be 15th February, 1984, shortly before 7:30 in the evening:

Tegan: My Aunt Vanessa said when I became an air stewardess "If you stop enjoying it, give it up".
Doctor: Tegan...
Tegan: It's stopped being fun, Doctor.

Incidentally, Aunt Vanessa's advice is good.

While the show will never have the same magic it did with the 60's and 70's, I've been enjoying Moffat's run significantly more than I ever did RTD's. The RTD era just left a bad taste in my mouth and I struggle to sit through most of those episodes nowadays. The current show doesn't hold a handle to the days of Jon Pertwee and Tom Baker but in my opinion has vastly improved with Moffat at the helm and makes for some brilliant TV viewing.

Wise words Vopiscus / Auntie Vanessa.
Incidentally, Tegan's leaving scene was done twice, as the first take was deemed too emotional, as Janet Fielding was in tears, kicking bits of the set. Once everyone had calmed down they retook it. A friend of mine was on set that day and told me that it really wasn't an easy day.

Wow. Did she not want to leave then?

I don't know what your definition of fun is.
It's adventures in outer space traveling in a spaceship and meeting aliens. What's not fun about that?

It depends on what you mean by fun, because Ant and Dec and the Chuckle Brothers could be described as 'fun', but that's not what I'd want in Doctor Who.

I like your fun joke that Capaldi sucks, because we can laugh with a knowing wink that you're being ironic as we know the opposite is true.

Anything but Ant and Deck...

I think some people may genuinely hark for the days when Mickey would fall into a wheelie bin or run into a wall because he missed the Tardis.
Or they do that joke when the Doctor and his companion run to the right of the screen, then to the left, then opposite ways, then suddenly run together across the screen with the monster chasing them.

LOL I remember that, what a muppet!

I think it was simply a very stressful day and various tech problems had left them with very little time to complete that studio session - so nerves were frayed and emotions were running extremely high.

I think it stopped being fun in series 6, but inertia carried it through series 7. The split seasons distracted from the issue, whilst the 50th and McGann's return injected a brief sparkle back into the show. Smith's swansong was exciting as any regeneration episode is, more so in the light of Malcolm Tucker being announced as a replacement - something which many people equated to a radical departure in the overall style of the show., especially once the first Pertwee-esque photos and comments about the future emerged Frankly, I can very easily imagine all of Capaldi's episodes starring Matt Smith instead. And that firmly includes Capaldi's rant about using the Osgood boxes.

It was a great scene, and I hope there's more of that sort of thing to come. But I can imagine Smith delivering it just the same, as though the production hasn't really changed for Capaldi. Unless you're easily amused by sonic glasses and guitars.

So when you said...

Also now this series two parters are being added left, right and center just because the fans said so

What did you mean exactly?

Don't know what you're talking about :/

It is still fun

Dr Who has never been fun and only an idiot who makes sexual advances towards office furniture would think it ever was.

What is has always been has been a show that mixes serious drama, history, sci-fi, fantasy and dry British humour into a melting pot and the show has been the result.

For example, Genesis of the Daleks was a seriously dark episode where the Doctor had to wrestle between whether to destroy the Daleks at their birth or not.

If you are talking about the Doctor then Tennant's gurning could get as annoying as Capaldi's guitar and Matt's fez.

For reference people were moaning/attention seeking like this since the sixties if letters to the BBC in the Dr Who encyclopedia is any guide.

Christ on a bike - that's why I stay away from you nerds and your "he really means..." "let's interpret things so we can be outraged or plug our own agenda" crap.

DID I MENTION POLITICS? NO - I said, "when did it stop being fun" - nothing else, no subtext, no hidden agenda, no "reading between the lines, perhaps he meant..." crap.

I'm nearly 50, I have a life, I had over half of it now (probably) for God's sake. I don't live with my parents (as i suspect some of you still do...) I've been married a long, long time and run my own successful business. I don't need to be preached at on Saturday evening

I asked a simple bloody question! So - just when did it stop being fun??

Did you forget that saladfingers were on these forums for a moment?

A nerd writes:

Another poster * mentioned Politics, LCDMAN. The response you quote above wasn't aimed at you.

Already given my answer; it hasn't. IMO. So will butt out now!

(ETA * It was Brandon, actually. But he might deny that )

No he didn't

(sorry, couldn't resist)

Do you live in another Country its Sunday?? But to answer your question its fun but not as it was before

Do you live on another Planet - maybe Uranus?? (as in up your...)

Just when is DW on TV FFS? Saturday.

I realise now why I stay in the real world, and not this forum - adios nerds......

It really can't be good for a person's blood pressure...

Then next time include that? "I don't need to be preached at on Saturday evening" thats kinda misleading :/

Nice insulting little flounce there! I guess not enough people agreed that the show wasn't fun anymore?

Me or?

I understood him perfectly, especially in the context of his opening post.