Depending on my health, it is usually one or two hours every day for me. Others I know only work on their novels on weekends since they don't have enough time during the week. Unless you're referring about "professional" full-time writers who don't need to work another job to support themselves and their family. Then they usually write from morning 'till night with some short breaks.
But even they sleep sometimes...
The truth is that we can never know how much time people really spend writing because not all of them take notes or record their ideas so they can go back to them later. But most likely between 1,000 and 6,000 words per hour can be said to be an average rate for a person who is able to concentrate completely on his or her work.
And yes, most writers I know are actually very busy people too. While some of them may have more free time than others, none of them has any more or less than anyone else. We all have other things in our lives besides writing. Some of us have families to take care of, others have other jobs or activities they enjoy doing, some have hobbies or interests outside of writing. It's just part of being human that we don't all have exactly the same amount of time each day.
However, as long as you are willing to put in the effort necessary to write every day, you will eventually find ways to make time for it.
Every morning, I spend one to two hours writing. That evening, I might spend an extra hour revising my work. Other authors I know write intensely for several months before taking a few weeks off. Then they start again at the beginning of another year.
I used to think that artists worked in bursts, only stopping when they ran out of ideas or had enough money coming in to not have to work for a while. But people who love what they do will always find a way to keep creating art - we just need time to develop our projects and get them out into the world.
Writers work in streaks. Days may go by when I don't write anything new due to life getting in the way (or because I don't want it to). But then I'll hit a point where I have so much material that I can't decide what story to tell next, and those gaps seem like perfect opportunities to me.
Some years are better than others. If I'm struggling to come up with ideas, I may wait until I have several that I feel confident about, then I'll write one that doesn't require as much research or fact-checking first. This usually leads to a more satisfying story that leaves me with time and energy left over for several subsequent ones.
So, if non-pleasure reading is included, it's closer to 20 hours a week. I'd probably do anything from a half hour to two hours every day, for a total of four to ten hours per week, which is a large range, but it all depends on what else is going on. I'd estimate I read a regular 300-page book in a week on average. There are more interesting things going on in the world than literary fiction!
If you exclude pleasure reading, then the figure drops significantly. I know that when I'm not feeling particularly interested in something, I'll usually only read for about an hour at a time. So if you assume an average book length of 200 pages, that means you'd be reading around 40 books a year, which is not very many.
However, this figure doesn't take into account how much you might want to read for research or education purposes. If you're doing a degree course, for example, then you'll probably need to read more than just fiction. It could be argued that scientists and historians also read for entertainment, though!
In conclusion, people who say they don't have time to read should really think again. It can be done in a few hours a week, even if you're not including pleasure reading.
For example, if your weekly goal is 3,000 words and you have five pieces of time set out to write each week, you'd need to write 600 words every day to meet your weekly target. I write for 1-2 hours in the morning before doing anything else. It helps if you're not afraid to put yourself out there and try something new.
The ideal time to write will vary for everyone. For me, it's early in the morning, when I'm not distracted by anything else in my life. But someone who works on their book all day long could probably get more done if they wrote then. The point is, find the time that works for you and stick to it.
Of course, writing a book is not just going through pages. You need to edit your work, decide what to keep and what to throw out, and finally publish it somewhere so other people can read it! All of these things should be done any time after you start writing the book itself.
The most important thing is to never let your writing go stale. Always want to improve your skills and creativity as a writer so you can make your book unique and interesting.
Finally, remember to have fun!
Some people intend to work on their dissertation for at least two hours every day, while others aim to produce two pages per day. Make a plan that works for you. I made it a point to focus on the writing and research portions of my dissertation for at least three to four hours every day throughout the period I was writing it. This allowed me to feel like I was making progress even when I wasn't able to finish any more than two pages.
In order to keep up with its rigorous publication schedule, some universities have developed policies regarding how long graduate students can work on their dissertations. The amount of time that can be spent working on the dissertation varies by university policy. Some institutions allow only two years to complete a degree, meaning that most students will need to find another line of work if they want to keep working on their dissertation after their initial completion date. However, many students are able to extend their deadlines through various means (such as taking classes during their dissertation year or finding part-time employment).
The length of time that can be spent working on the dissertation also depends on the type of project involved. If it is a large project with many components, such as a multi-year study, then the time limit may be five years from the start of the program. However, if it is a more limited project such as an original article or brief report, then only two years are required from the beginning of the program.