When to announce the wedding date?

Hello! My fiance and I recently became engaged. We have been talking about getting married in May 2020 for over a year. He is the youngest in his family and has two older sisters. I am 24 and he is 23. We both have good jobs and are completely independent. His oldest sister is very opinionated about long engagements and that there is no rush. His parents are also in this vein of thought. We are very nervous about how to tell them that we will be getting married less than a year after we became engaged. Has anyone been in this position before? What are your thoughts?