There are several synonyms to the phrase "days old" that can help us describe the age of an object or living being in a variety of ways. Some alternatives include "fresh" or "new" for things that have just been created or born. For slightly older objects or living beings, the terms "young" or "recent" might be more appropriate. Meanwhile, "infant" or "juvenile" typically refer to specific life stages of animals or humans. Additionally, "nascent" or "incipient" convey the idea of something just beginning to develop or emerge. Ultimately, choosing the right synonym for "days old" depends on the context and desired level of specificity.