How long + past simple, present perfect or present perfect continuous How long + past simple, present perfect or present perfect continuous. How the meaning will be changed after using each of these tenses ? I don't know if I got it right, so I want to share the way I understand it and to be corrected if got something wrong. For example how the meaning will be different with this sentence: how long (work) for them. Past simple: How long did David work for them would mean that David worked for them previously but doesn't work for them anymore. Present perfect: How long has David worked for them would mean that David works for them generally and I'm asking how long does he do it? Present perfect continuous: How long has been David working for them would mean that David works for them at the time of speaking? I have doubts about the Present perfect and the Present perfect continuous. I think didn't understand them correctly.