It’s best practice to put the actual ceremony time on the invitation. Most guests will plan on arriving between 15-30 minutes before the start time. If there are cultural norms where guest show up later than the time indicated, or the venue is difficult to find, you can push the ceremony time on the invitation up by 30 minutes. However, make sure you provide refreshments and plan on your musician starting when the first guest arrives. Some guests may be arriving an hour before your actual start time!