Is 20 months to short to achieve a 1st dan in TKD? ( 5 Hours a week of training) (4 days a week)?

Absolutely it is too short. If a school (mcdojang) does that you need to find another school.

Edit:

Earning a black belt is not about time. There are many I would even say most never earn it. There are many with one today that didn't earn the one they are wearing. It takes a lot of patience to really earn a black belt . It doesn't happen in 2 or 3 years. If you school is doing that I wouldn't attend there. I want to have more than a colored piece of cloth. I must have the knowledge and skill that is more important than a colored cloth.

Loyalty is great. However one must consider what they are being loyal too or why. I'm not in favor of divorces. But if the spouse was abusing the other I do not believe the spouse should stay in that relationship. Sure they can still love the person, but that doesn't mean the must stay together. I like being loyal to my employer. But if there is no opportunity for growth or anything that benefits me it would be time to move on. The same thing with martial arts. If you do not have high enough standards in your school you can't grow to where you need to grow as a martial artist because it is not be developed. Therefore it is up to you to make a decision to be loyal and stunt your growth or to be wise and find the best instructor that will help develop you and push you to be better than themselves. If garbage goes in you can only get garbage out. I'm not saying your instructor is bad. I don't know the person or their skill. But if the standards are as low as you are giving us that is a huge red flag. You can't raise the standard if you don't know what they are or what they should be. It is more than saying if my student are going to get a black belt they it will take on an average of x amount of time. I had to wait 2 years and they will have to wait 3.5 years. That is not how it should work.

My suggestion is to go visit some other schools in your area. Style doesn't matter. Then compare the quality of instruction and the skill of the students. You should begin to notice the differences. If you see high ranked students with little ability you will know that is not the best place. But if you see low rank students with a little skill and noticeable differences with the students with higher rank and highly skilled students with advanced rank. That school is a better option. Who knows that could be your school. But make sure you have an open mind when you visit those schools.

Many of us that has been around a long time have seen students that have come from other schools and have rank that is quite obvious to us that they do not deserved or have not earned. We have had brown belts and higher come in and know less than our white or yellow belts. Personally I feel sorry for them as they have spent & wasted money and time that they can never regain. The good thing is that they had the opportunity to change and improve if they desire. They must be willing to let go of the bad habits they have already formed from their previous experience.

Yes; most definitely. There is more to being a legitimate black-belt with some ability than just training-even if you are training 5 hours a day, 4 days per week. Beyond that there is what I call the experience factor and 20 months is just not enough time to acquire the experience and knowledge that goes with that experience really. Anything less than about 5-7 years is inadequate. While you might have after 20 months the skill and ability to defend yourself against others that know little or nothing or are not tough, experienced individuals you will probably find it inadequate beyond that. The ability to deal with those beyond that category only comes with more time, more training, and more experience than what one can acquire in just 20 months. At the same time though it is a start.

Yes. That is less than two years. I train 5.5 hours a week. I am currently 3.5 years into my program, and I'm still 3-4 years away from black belt. When I was two years in, I promoted to the first intermediate belt. And I can tell you that my biggest period of growth happened at that rank, between years 2 and 3. Even though I am confidently solid on the vast majority of my curriculum, I still have a lot of room for improvement. People like to dismiss black belt as, "just understanding the basics." Yes, ok. But there's more to "understanding the basics" than simply going through a series of movements. When you achieve black belt, you should also be able to execute skills with power and clean technique. And having high standards like this is hard to find with martial arts schools these days.

Unless you have a great deal of past experience in similar arts/styles and are an exceptional student, accomplishing the earning of the rank of 1st dan in less than two years would seem unrealistic.

Us old timers in the martial arts spent 5 to 10 years to receive a black belt and the training was much rougher than the average today. Seven years seemed to be about how long most of my contacts spent getting their black belt. It took me 7-1/2 years of hard work. I received that black belt in 1975. In those days promotion was about knowledge and ability. Today it is about promoting student often for two reasons. First, students that don;t get promoted often get bored and quit. Second, promoting students fast keeps them busy and paying for classes and testing. Black belt testing in the 60's and early 70's was $15 to $25 on average. Today they charge hundreds of dollars for testing because people are stupid enough to pay that much.

Its all about quality over quantity my friend, that is too much of a short time frame, yes it is correct repetition is good , but its only worth it if you have correct technique and tuition.

Yes.