That Deathday Party, then, must take place in 1992.

While this seems pretty cut and dried, this date doesn't agree with the date given on the Deathday Party cake.

If we accept the timeline derived from the Deathday Party cake, Harry is telling Sirius about this incident in July of 1994, a half-year earlier.

And if he's that foggy on dates, maybe his Deathday shindig was wrong too.

To those I recommend using the Deathday Cake dating.