This is personal. Some people buy it when they propose, some people buy it before they get a license, and some people buy it before the wedding, depending on their own arrangements.

It is advisable to wait until you get the finished product after buying a loose diamond. If Jietuo is available, it will take about a month to get the ring. If you want to use it on the wedding day, you should order the diamond ring at least one month in advance, just to be on the safe side.