What do you mean by learn? As an end-user or coder?
If you are familiar with any language, c/al won't take time at all to learn because it's so very simple and basic. It's basically IF,THEN,ELSE,BEGIN,END,CASE,EXIT... now you know c/al
In all, including functional knowledge and .NET interoperability, I would say 3-4 months.
However, your question is not easily answered. C/AL Syntax is quite easy - but as a programmer you also need to know how the standard works and how it does things.
So if you ask me - im working with NAV for around 4 Years now, and im not done discovering new things by any means.
I think EvR is significantly over-simplifying here. That or I take a much broader view on your question. I tend to go more with Wisa123's answer. Yes, you could read all of the manuals, do the labs in the training material, etc. in a couple of months. But do you really know NAV at that point? I would argue no.
And you do need to understand the functionality before you're ever going to be a good developer, if that's what you are aiming to do. Regardless, NAV is big enough now as a product that it is not reasonable for a single person to know the ins and outs of every little thing.
Answers
If you are familiar with any language, c/al won't take time at all to learn because it's so very simple and basic. It's basically IF,THEN,ELSE,BEGIN,END,CASE,EXIT... now you know c/al
In all, including functional knowledge and .NET interoperability, I would say 3-4 months.
https://msdn.microsoft.com/en-us/library/gg502499.aspx
However, your question is not easily answered. C/AL Syntax is quite easy - but as a programmer you also need to know how the standard works and how it does things.
So if you ask me - im working with NAV for around 4 Years now, and im not done discovering new things by any means.
And you do need to understand the functionality before you're ever going to be a good developer, if that's what you are aiming to do. Regardless, NAV is big enough now as a product that it is not reasonable for a single person to know the ins and outs of every little thing.