How do you use "Since when did you...?" AND "Since when have you..."?
How do you use tell apart when to use these two? I'm really confused.

Since when have you been standing here?
Since when did you get here?
Since when did you start smoking?
Since when have you smoked?

Thank you.

Question

How do you use "Since when did you...?" AND  "Since when have you..."?
How do you use tell apart when to use these two? I'm really confused.

Since when have you been standing here? 
Since when did you get here? 
Since when did you start smoking? 
Since when have you smoked?

Thank you.

Answer

In British English, at least, the difference is one of emotion and emphasis.

Since when have you smoked? is a serious question expecting a factual answer. A doctor might ask you this.

Since when did you smoke? Is an expression of surprise  - your mother might ask you this if she caught you smoking for the first time, she probably doesn't care when you started.

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