Wedding invitations rarely spell out exactly what to wear, so the details do the talking. An evening ceremony at a formal venue calls for a full suit, dark tie optional. A daytime garden wedding gives you room for lighter fabrics and a more relaxed blazer-and-trouser combination.
The rule that rarely fails: dress one notch more formal than you think you need to, then adjust down if the setting clearly calls for it once you arrive. A well-cut blazer in a neutral tone is the safest anchor piece for almost any wedding you'll attend this year.