"BITD" is an acronym that stands for "Back in the Day," which is often used to refer to something that happened in the past. However, there are several synonyms for BITD, which can be used interchangeably in conversation or writing. Some of the popular synonyms for BITD include "in the old days," "back then," "once upon a time," "in the past," "historically," "earlier," "long ago," and "once." These synonyms can be used to add variety and nuance to a sentence or story to describe a past event or memory. Additionally, using different words can emphasize a particular aspect of time, such as nostalgia, significance, or distance.