please tell me the approximate time of this meeting when you are available The problem with the way the sentence is written is the last clause "when you are available" 'available' means able to attend the meeting / available (free time) to attend. But I think you mean 'please tell me the approximate time of this meeting when you have time. 'when you have time' is a short form of saying 'when you have time to reply or time to tell me the time of the meeting.' If you are asking the person to tell you the time that they would be available to attend the meeting (when they are free to attend), then you would write: - please tell me the approximate time that you would be available to attend this meeting. Hope this helps...

In practical life, we just ask, "What time is the meeting?" That's it. We don't go into all the extra frills. What's the point? If we want to know when the other person is available for a meeting, we just ask, "When are you available for a meeting?"

Not correct. But not sure what you are asking: Time of meeting? Or whether the person is available?

Wendy... I had an afterthought = I thought of something else that I should have written in my answer. We often use the expression 'at your convenience' which means 'whenever it is convenient for you to respond/reply/attend/do something etc. So the sentence could be written as "Please tell me the approximate time of this meeting, at your convenience." OR "At your convenience, please tell me the time of this meeting".