When did Lien start her hobby?

Two students were asked about their hobbies and here is what they said.
Lien: Cooking is my favorite hobby. My grandmother taught me how to cook my first dish when I was 8. My family enjoyed it so much so that is when I started this hobby. Some people say cooking is a waste of time but I find this hobby very interesting and meaningful. I really love trying new food and cooking for my family. The feeling of making my family happy with my food is amazing. I often collect recipes from my mother and my grandmother. Sometimes I also get recipes from the internet. Then I write them in a notebook. I hope I will become a good chef and have my own cookery book in the future.
Cuong: I have an unusual hobby: carving eggshells. I started this hobby four years ago after getting a carved egg from my dad when he came back from Japan. It's amazing that something as fragile as an empty eggshell can be made into such a beautiful piece of art. I was so amazed that I learned how to carve them myself from the internet. I find carving eggshells a little difficult but so interesting and useful. The feeling of accomplishment when I finish a piece is absolutely awesome. This hobby also helps me be more patient and careful.