In game calendar only shows 14th - 18th anniversary events starting on 16th March with the earlier anniversary events starting a month or so later.
What makes you think there'll be a 19th anniversary? Always optimistic? But if it happens, it should start mid-march too. As usual. I guess they've just not put it into the patch yet, and therefore /calendar did also not get new info.
They already said they are working on 19th anniversary events As for Calendar you prob wont see it till the March Test patch, unless they announce dates before then So probably check back in 2-3 weeks