In days past is a phrase that refers to a time period in the past. However, there are many other synonyms that could be used instead of this phrase. Similar expressions include "in the olden days," "in the days gone by," "in the bygone era," and "in ancient times." Each of these phrases conveys a sense of nostalgia and a longing for a time that has now passed. Moreover, they can be used in various contexts, ranging from informal conversations to formal texts. In summary, there are many synonyms for the phrase "in days past," and using them adds richness and variety to our language.