The state of boy/girlfriendshipness must be formally announced, ideally through a public advertisment in The Times, but these days more commonly on the official web-based boards set up for this purpose.
I always understood the situation to become officially acknowledged when, and only when, you were finally caught out behind the bike shed. Or adult equivalent, I suppose, in this case.
I think that it's when engaging in romantic liaisons with a third party would be frowned upon by the other person. Unless they're involved as well, of course. That's an entirely different matter.
Penelope is proud to announce that after many years of searching, she has found a man with sufficiently low standards to happily accompany her for cocktails, noodles, full English breakfasts and participate in the odd snog. [Rab] will that do?
I too enjoy "odd" snogging. It has been a cause of much friction between Mrs Stevie and me, but only when she's asleep as she finds the whole thing a little strange (or as she would jokingly put it "Get the hell away from me you twisted goon").
*Dances round with a multitude of glee at Pen's excitement and sings 'Hurrah, Hurrah, Hurrah!* Well Done hon! Also keeping fingers crossed, just incase!
Goodness! It must be - er - something to do with autumn. I'm very pleased for you all, and kind of jealous, which is odd given my non-single status. There's something thoroughly pleasant about starting going out with someone that is intrinsically better than actually going out with them, however nice and fulfilling the latter may be. I'm sure Aristotle had something wise to say on the subject.