"Realize" and "Realise" are the same word. The first one is American spelling and the second is British.
Realized and Realised are the past tenses of the first two.
"Now, I realize how much I need to study." In this case it means to "understand" or "become aware."
"His goal of learning English is finally realized" In this case it means "completed"
Your sentence is not the correct usage of the word realise.
It would be correct to say, "The first time I met him was on Friday, April 29, 2001."
You could also say, "The first time I realised he was there, was on Friday, April 29, 2001."