Phrases Apologies and Excuses

I didn't realize...

Meaning

Explaining a lack of awareness.

John: I'm sorry I was late.
Alice: It's alright. But we were waiting for you.
John: <b>I didn't realize</b> how late it was. Sorry for that.
Alice: It's okay this time. but next time please be punctual. <b>I didn't realize</b> how much time you need.