auxiliary verbs - "did you" vs. "do you"

What is the difference between "did you" and "do you" in the following two sentences:

Did you want to schedule a meeting?
Do you want to schedule a meeting?

I can't understand this usage for "do you" and "did you" which seems to be very common. Clarification is appreciated!

Answer

"Do you want to schedule a meeting?" is very straightforward. It is inquiring if the person wants to schedule a meeting.

"Did you want to schedule a meeting?" is more complicated and the meaning can change depending on the context as well as the inflection.

It could be inquiring if what you did was actually what you intended to do.

Sir, I'm calling from the bank. We noticed you scheduled a bill payment of $100,000. Did you want to schedule it for that much?

It could be asking what you want you want. Essentially synonymous with "do you"

Sir, I'm calling from the bank. I got your message to call you about the loan we discussed. Did you want to go ahead and proceed?

It could also be discussing something you weren't able to do and inquiring if you had wanted to.

You seem upset that we went to the movie last night while you were at work. Did you want to go with us?