What I found interesting about the day in Japan was that all the European ladies were wearing hats but from the Middle East onwards, none of the ladies were wearing hats.
But then the Scandinavian royals have events every year which call for this particular sort of "daytime super formal" wear and they are used to it. It's a tricky one as you have to wear a long formal gown, but you can't look eveningy in any way, so you have to be careful with fabric choice and sleeve length and you have to wear a hat cos it's daytime.
There isn't really an equivalent in the UK. The only thing that's super formal during the day is the Opening of Parliament and its a tiara/full satin and white furs event.