Well, you can do a template in about 30 seconds if you really want to, but it might be a bit plain.
Really, this is like asking how long a piece of string is, as each template is different and has different requirements, and may take more or less time depending on your skill level. Maybe if you showed a specific template people could estimate how long it might have taken them to produce.
How hard is to make a web template?I know it's different for everyone,but I just wanted to know how long does it take to make one web template?
A basic kind of a template could be made in a couple of hours. Say where you just have a basic layout - 1 column, 2 columns or 3 coulmns.
However, if you decide to add more functionality or style to your template, it would start taking more time. For example, if you decide to induce cool Jquery effects or CSS3 effects, then it would take more time.
It takes a few hours to make a decent web template, and up to a day to make a great web template. That also depends on the designers experience. Generally, the more elements and detail you put into the template, the longer it is going to take.