Sherlock doesn't register the date until he catches sight of John's photograph plastered across the front of a tied bundle of garish gossip rags, during one of his rare visits to London. The photo was obviously shot secretly and from a distance, across the grey winter vista of the graveyard. John is using his cane again, apparently, and the sight of that feels rather like a sharp punch to the solar plexus.
FAITHFUL FRAUD, the bold headline shouts, and beneath: John Watson's Teary Birthday Visit to Fake Genius' Grave.
Teary doesn't accurately describe the stony, pale expression John is wearing, but that hardly matters; it's not as though Sherlock expects even a passing degree of accuracy from the press.
He does realize, however, that he never spent a proper birthday in John's company, which seems strange for a reason he can't quite pinpoint. Sherlock hasn't marked his own birthday in years, but it is precisely the sort of thing that John would have latched upon as an excuse to drag him to a restaurant and cajole him into a meal.
Now, six months removed from that annoying pecking to eat, from the harping to keep his mould cultures and specimens on their designated shelf in the refrigerator, and from the taste of tea made strong, hot, and perfectly sweet and milky... After six months away from John, Sherlock can feel the lack, tightening his skin like dry air and making his fingers twitch and dance without pattern or reason. It is intolerable, to be so affected by sentiment— and here, six months without hearing John's laugh, Sherlock will not deny that's precisely what this is. Sentiment, insufferable weakness, latched like meathooks into his chest.
He steals a copy of the tabloid, an unseen shadow in the wee hours, and tears out the photograph before binning the rest. He doesn't bother reading any of the drivel attached, simply folds the picture carefully and tucks it into the pocket of his shabby anorak.
It can be helpful to set a goal, after all. A realistic deadline to keep a plan on track, and to encourage forward momentum.
Sherlock is determined to spend his next birthday at 221B.