One day, and it is the day of the procedure rather than the day of the prep. The harder question is what you have to tell people, and the answer is less than you would think.
One day. You can't drive or work after sedation, so even an eight in the morning slot costs you the whole day. Most people are back to normal the next morning.
Most people work it. You're on clear liquids and the prep doesn't start until the evening, so a desk day is fine if you can leave on time. Physical work on no food is rougher. And once the prep starts you need a bathroom within about a minute, which rules out a lot of jobs.
No. Sedation blunts your judgment for longer than it makes you sleepy, which is why discharge sheets rule out driving, signing things and decisions that matter. Feeling fine isn't the test.
Usually not. They need to know you have a medical appointment, roughly how long you'll be gone, and that you can't drive after. None of that means naming it. Check your own policy, but the reason is rarely the part anyone asks for.
Ask for their earliest slot, or a Friday. An afternoon procedure means a longer fast and a prep that runs into the morning, so it is the harder day, not the easier one.
Only if you let it. A calendar entry doesn't have to say what it is, and neither does a note to your team. The reminders this site builds are worded so nobody reading over your shoulder learns anything.
Build your own plan