I have a question to which I get different answers from various people and I am approaching you as you will give me the right answer ... My son was born and studied in Kuwait ... and has arrived back after completing his college education ... as they don’t give residence for boys after 21 yrs of age, he arrived on Aug 30 on a family visit visa which says valid for stay upto 3 months. I have booked his departure from Kuwait for Nov 29, evening flight. Can you please advice me if the date for departure is okay or he should leave the country 2 days earlier as I don’t want to pay any fine and the immigration blacklists people for overstay. Do they calculate 90 days ... or 3 months?

Name withheld

Answer: Yes, people are blacklisted for overstay — not only the visitor but also the sponsor and they can’t get any more visit visa.
The last date is definitely Nov 29 because the visit visa is valid for 3 months and not 90 days, regardless of the fact whether a month is 28, 30 or 31 days.
So, your son can leave by the evening of Nov 29 but as a precaution it is always better to leave a day or two earlier to avoid any problems ... like cancellation of flight or any other cause of delay, so that you have a few days to react.