Dividends have been tough to figure out. There isn't a list of LDTs I can grab on a website. I did manage to find most of the ex-dividend dates. AFAIK if you hold shares before the ex-div date you get a payment. OMLs ex dividend date was the 22nd, so even though it was after LDT, they did technically own the shares at the right time...
I'll go with thoughts from others here?
Unless I find a site offering all those dates, the only way I could see of having things perfect would be to have humans entering the dates for me. Perhaps double checked by someone else. That way contestants would have to enter the LDTs and ex dividend dates.