la antevíspera - day before yesterday, second day beforeSpanish example: Recuerdo la antevíspera de la Navidad de 1946.
English example: I remember the day before Christmas Eve of 1946.
Source: la antevíspera - day before yesterday, second day before (https://www.123teachme.com/spanish_feeds/word_of_the_day/2020/8/21)