Knives should be sharpened every 1-2 month.
How do I know I need to sharpen my knife?
First sign is that the blade feel dull. You can carefully check that with your finger tip. Next, try to cut a piece of paper with the dull knife. If it doesn’t cut the paper easily, the knife needs sharpening. In the kitchen, the big test is often the tomato. If your kitchen knife smashes the tomato, it is time to sharpen the knife. A well-sharpened knife will slice cleanly through the tomato without must down pressure. If the blade catches on the skin for example, your knife is dull. Another good test is if the knife slips off an onion, and not slice straight through the skin it is a dull knife.
Dull knives can be dangerous as well. A knife that needs sharpening can slip and cut your hand.
Sharpening tools. There are many ways to sharpen a knife. The most common of course is the rod. Other methods include knife sharpening tools and sharpening stones.
Recommended Knife Sharpening Tool