I don't know, unless it's an Arabic date. It doesn't mean anything in terms of Spanish history, so far as I know.
The AQ communique mentioned three attacks - the "train of death" (Madrid), a "black smoke"(?) and finally, a "winds of death."
The "black smoke" is next, then. The only thing that "black smoke" brought to mind was the Vatican. This is because after the Pope dies, during the election process, the ballots are burned after the voting and a chemical is applied to make the smoke black if no pope is chosen. When one is chosen, the ballots are burned without the chemical and the smoke is white. So I was wondering if it could possibly indicate an attack on the Vatican or on Rome, since Italy was one of our allies.
Or, again, possibly an attack on Gibraltar at the end of April, which would be an attack on Britain and also have the effect of blocking access to the Mediterranean (and which AQ has attempted on earlier occasions).
I think that Italy would also be weak, in terms of security and in terms of popular willingness to stand up to an attack. As for Britain, I don't know - the Brits (particularly their treacherous leadership and media) were very opposed to Blair's support for us, but I think they might actually come to their senses if they were attacked. So my money is not on an attack on Britain - yet.