Hmmm, one month for the first draft you mean? That's certainly possible if I have no interruptions. Then I'll put the manuscript aside for about a month, and do a second draft to sort out any problems with the story/characters etc. This rewrite stage can take me anything from another month to three months, since I make quite big changes at this stage.
After this, I put the book aside again (ideally for 2 months at least... though I might make a start on the first draft of the next one in this time, or be doing promotion for the last one). Finally, I do a third draft fixing up the smaller things, and then go through the text one last time with a careful proofreading eye before sending it to my editor.
If I'm publishing traditionally, the manuscript then enters the editorial process at my publisher, which means more tweaks to the story/characters, and then another round of copyediting and poofreading working with my editor before the book finally makes it into print, usually about a year after delivery. (Publishers need 6 months at least to launch a new title properly.)
Publishing direct on the kdp might make the publication process faster, but I think the rewrites and "resting" stages are still important, perhaps even more so since you haven't got an editor. So far I've only published my rights reverted titles on the kdp (which have already gone through the editorial process). If I do a new title, I think I would hire a freelance editor to help me. But that might be because I've been publishing traditionally for so long that I have lost confidence in my own work... it's been my experience over the past few years that a lot of writing time is wasted doing queries/propsals for new projects and writing half-books that never make it into the traditional publishing system because publishers "don't see a market for it". At least amazon's kdp lets us publish and find out if there is a market for our work, which is more democratic than an acquisitions meeting - though I think the percentage of titles that actually sell enough copies to make publishing them worthwhile will prove just as small!
Usually 2 months to do a 70k book, then full three months of editing. My recent book, which has been my fastest ever, took me only a month at 60k words. Still, I don't believe I'm very fast. However, I do write every single day without fail.
I can usually write the first draft of a novel (90k to 160k) in a month to three months, but, as others have said, it's the "resting" period and the revisions that take the time. That for me, so far, has been anywhere from a couple months to a few years, depending on the book and the genre.
Takes me about three months to draft a novel, then about two years to get around to editing it. I'm actually just starting to edit a novel I wrote in 2004. I remember writing it, finishing it, not being all that happy with it and just forgetting about it. Figured I'd have another crack at it as the manuscript should have "matured" enough by now ...!