Your save-the-dates and invitations should reflect the formality of your wedding and who you are as individuals. If you’re having very casual nuptials and your fiancé never goes by his given name, it’s perfectly acceptable to put the nickname on the save the dates. If you’re unsure, however, air on the side of formality. Using your full names adds a feel of ceremoniousness and helps convey the magnitude of your wedding. In fact, the general rule of thumb is to spell everything out fully—names, street addresses, and times, for example.