There is no firmly scheduled time for the Bank of Japan announcement and statement. It's a good bet to expect it sometime in the 0230 to 0330 GMT time window based on past experience.
The but is the longer it takes the more likely there is to be some sort of substantial change. The logic being that for something big there is more discussion and debate and hence it takes longer.
I posted earlier:
Given the time, its now 0325 GMT, is there something else, something bigger, coming?
