This entirely depends on what level you are starting at and what you are using to train the skill.
out of those, woodcutting.
It takes a week and a day (source) 99 Woodcutting :D
About - 1 Month?
It depends on the average hours you spend wc'ing a day.
That would most likely take around 1 - 2 years.
It would take a while. You would have to chop about 63,000 yews. Check out the the link below.
level 99 woodcutting.
Go to runehq.com they will tell you everything you need to know.
Woodcutting can be trained by cutting down trees, chopping ivy, and various other methods.
I bet a few hundred people are pondering over how long it will take. From 78 Woodcutting to 99 Woodcutting can take from months to weeks, depending on what you want. You either can go for Money or Experience; Ovbiously everyone would want Money, However! The money way will take any where from 3months to a year. The easier route (That would make more money in the long run) is Ivy the 2009 Update, currently the fastest way to 99 Woodcutting. Requiring 68 Woodcutting, it is VERY popular. This is the best route.
you will be looking at around 6 - 8 months, maybe longer.