220.127.116.11 Event Properties
Two events are associated with a contact: a birthday and an anniversary. Each event is defined by two properties: a PtypTime property and an object PtypBinary property. If one of the two properties is set for an event, the other MUST also be set. If either of the two events is defined for a contact, the PidLidReferenceEntryId property (section 18.104.22.168.1) SHOULD be set to the EntryID for this Contact object.