I know it depends on something something but let me give you a general view to acquire the basic forex knowledge like Babypips course. If you are working day job, and can study 6 hours a week then probably 6 months. Or 12 hours a week for 3 months. Now you can calculate based on your leisure time. But that's not all. Once you understand the whole process of Forex, it's just a beginning. I agree with @tomorton that it takes forever to study, you have to be completely immersed when you want to enter forex. It would become useless if you enter and stopped in between. All the best!
Right! And the actual journey starts when after learning the time comes for implementation in the real trading world.
Define what you need to learn to be profitable. Learn it. Ignore the rest. Objective 1 is identifying a trend, 2 is mastering risk management. That's it. Three days learning, then move on to demo for a month.
If anyone really interested and want to learn forex trading with full of dedication, then within 6 months he/she will learn