Other forms: eves
An eve is the day — or night — just before some event. You might call the day before your birthday your "birthday eve."
Some holidays are well-known for having the proceeding days distinguished as eves: many of us celebrate New Year's Eve, others gather for meals on Christmas Eve or Passover Eve, and the word "Halloween" comes from "All Hallow's Eve." The word eve is sometimes also a shortened form of evening, the last part of the day: "It stays light so late on a summer's eve."