“Oops! I meant 2 weeks from yesterday, not today.”

You sent out an informal e-mail to a group of friends telling them about a camping trip you want to invite them all on. After you sent it, you realized that you wrote the wrong date. You send out another email to correct the mistake:

Oops! I meant 2 weeks from yesterday, not today.

Oops!

"Oops!" is something you say when you've made a mistake, dropped something, etc. It's an informal expression and sounds a little childish, so you wouldn't use this if you've made a really serious mistake.

I meant (something)

Use this phrase to correct something that you've said or written that was incorrect or unclear. For example, if you told someone that you'd "meet them outside" to go to lunch, but didn't specify which building you meant - outside your office or theirs - you can say this when you see them outside your office:

Oh, hey! I meant "Meet me outside your office."

(# of weeks/months/years) from (a day)

People often use expressions like "in 2 weeks" approximately. So it can be hard to know if someone means exactly 2 weeks or about 2 weeks. When you want to specify an exact day, use phrases like "a week from tomorrow" or "two months from today":

The school dance is only a week from tomorrow. Do you have anyone to go with?

This works for talking about the future. Talking about the past uses a different phrase:

We first met four years ago today.