The length of your skirt depends first and foremost on the amount of leg you are comfortable with baring: the less comfortable you are, the longer the skirt.
Trends are all very well, but it is important to choose your skirt length according to your legs and body shape.
If you have thin legs in proportion to the rest of your body calf length skirts will give you the appearance of more muscular legs. Choose a skirt that ends at the thickest part of your legs.
If you have heavy legs, ankle length is the way to go. If you are choosing shorter lengths, make sure the skirt does not end at the thickest part of your leg, which will make it look heavier.
If you are tall and have those endless legs (Wow!!), skirts a little above or below the knee, and anything longer at all would suit you.
If you are short, with short legs, you can wear trim short skirts well above your knee to make your legs look longer. fitted short skirt would showcase short legs perfectly, making you look taller at the same time.