Although the question wordA word that introduces a wh-question. E.g.: What are you doing? since when is normally used with the present perfectThe aspect expressing completion. E.g.: He’s finished university., with present simple it expresses annoyance.

Since when are people like Geoffrey allowed to join this club?!

We use the present perfectThe aspect expressing completion. E.g.: He’s finished university. continuousThe aspect expressing duration, formed with be + verb-ing. E.g.: What are you doing? tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. for actionA general term expressing that somebody or something does somethings which started in the past and are still in progressAn action is in progress when it is happening. E.g.: When I arrived he was surfing. ("he was surfing") in the present or have just finished.

I've been waiting for you for ages.
He has been living in that flat since last January.

If we want to emphasisSpecial importance or attention given to something. E.g.: All I wanna do is have some fun.e the length of the period of timeThe length of time between two points of time. that has passed since a past eventA general term expressing that somebody or something does something or that something happens. E.g.: An apple fell on Isaac’s head., an introductory it is used with the present perfectThe aspect expressing completion. E.g.: He’s finished university. tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses..

The prepositions for and since are often used with the present perfectThe aspect expressing completion. E.g.: He’s finished university. tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses.. For is used with an incomplete period of timeA period of time that includes the time of speaking. E.g.: I have known him for two years. ("for two years"), while since with a point of timeA particular moment in time. E.g.: She came home at six. ("six") I was born in 1980. ("1980") .