The phrase "olden days" is often used to refer to a bygone era, typically one that is viewed with romanticism or nostalgia. However, there are numerous other phrases and synonyms that can be used to describe this time period. Some examples might include "days of yore," "days gone by," "days of old," "days of antiquity," or even "days of legend." Each of these phrases helps to evoke a sense of history and timelessness, and can be used in a variety of contexts depending on the writer's tone and intention. Ultimately, the choice of synonym depends on the writer's individual style and the particular connotations they wish to convey.