尚未听说有严格意义上的“世界遗产日”,在教科文组织的工作框架内只有一个The International Day for Monuments and Sites(国际古迹遗址日) 接近或informally known as the World Heritage Day.
不过它应该是在每年的4月18日。因为It was created on 18th April, 1982, by ICOMOS and later approved at the 22nd UNESCO General Conference in 1983.