YOU SAID:
Today's the day I say, on this very day, understand?
INTO JAPANESE
今日は私が言った日、この日に理解しますか?
BACK INTO ENGLISH
Do you understand today, the day I said?
INTO JAPANESE
私が言った日、今日は分かりますか?
BACK INTO ENGLISH
Do you know the day I said today?
INTO JAPANESE
今日言った日を知っていますか?
BACK INTO ENGLISH
Do you know the day you said today?
INTO JAPANESE
あなたが今日言った日を知っていますか?
BACK INTO ENGLISH
Do you know the day you said today?
That didn't even make that much sense in English.