We allow you to edit your own post within a five-minute window of posting. We’ve felt obliged to put in a time limit to avoid abuse, such as re-writing history. What you’ve said is what you’ve said.
If you’ve made a serious typographical error – bad coding, say, or typing “now” when you meant “not” – and the five minute window is gone, then email a Moderator. (Or, REPORT the post above or below yours, and be sure to be clear what you mean.) We’ll be glad to fix it for you.