There should be a nitice out on it the night before when the exchange reads out all the notices after the close. However it could be at the openingi and if it is then there will usually be about one or two hour delay for the pre opening before the stock actually starts to trade. At least thats the way it used to be when they had a actual trading floor. My guess would be nite before. Your broker should be contacting you especially if you have a large position in it. If he doesnt then you had better find a broker who is interested in your account