I have been on Clonazepam for a little over a month. I take 0.5mg twice daily. Once in the morning and once in the evening. You have to take medications like this daily at around the same time each day. I felt the calming affects within 5 minutes of taking my first dose and there on after. It works quicker if you do not swallow it. Just let it sit on your tongue and dissolve. It does not have a medicine taste. It is sweet with a minty taste. This is the lowest dosage by the way. I hope this helps.

From a bit of reading I just did - apparently it will work in a few hours, it is not the immediate effect type (so if you are having a panic attack you may need something different).
There was also this information about taking it.
Taking this Medication
Clonazepam comes as a tablet to take by mouth. It usually is taken three times a day and may be taken with or without food. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take clonazepam exactly as directed. Clonazepam can be habit-forming. Do not take a larger dose, take it more often, or for a longer time than your doctor tells you to. Tolerance may develop with long-term or excessive use, making the drug less effective. This medication must be taken regularly to be effective. Do not skip doses even if you feel that you do not need them. Do not take clonazepam for more than 4 months or stop taking this medication without talking to your doctor. Stopping the drug suddenly can worsen your condition and cause withdrawal symptoms (anxiousness, sleeplessness, and irritability). Your doctor probably will decrease your dose gradually.
(I did a second answer as I couldn't paste that info into the comments).
Good luck

I took it when I was ill to prevent me from having seizures...the calming influence was about 20 minutes after I took it...

clonazepam always took almost 20 or 30 minutes for me. there is a way for it to work faster. if you chew the pill it will work in a couple of minutes. have some strongly flavored juice or gum handy because the taste is terrible.

They usually kick in in about 5-10 minutes for me. They are made to work quick.

Oh, I know this medication. It takes longer than alprazolam or lorazapam to actually kick in, but it seemed to last longer. I'd give it about an hour.

I felt its effects in about 45 minutes.

I think it depends on the type.

My partner had some anti-anxiety tablets (for when he felt particularly anxious), and they worked within about a half hour, and then sent him to sleep, and he was extremely dopey afterwards. He didn't like them at all.

If they are the type of drugs that you have to take all the time (regardless of the situation), then after a few days you should feel less anxious.

It can vary depending on the kind you are taking.

about 30 min on empty stomach, sometimes knowing that you took it will make you feel calm psychologly, but I would give it about 30 min, then it really starts kicking in more and more for hours