When is the oldest melody from that you can sing from memory, without looking up the lyrics or sheet music? (except an actual music historian created this poll and is not going to let you answer with misconceptions)
*For instance, if you're going to answer "Renaissance" because you know Greensleeves, you should be singing it with the actual lyrics that were used by the broadside ballad at the time. If you sing the lyrics of "What Child Is This," then you answer "1850-1899" because that setting comes about in 1865.
No modern Christmas carols predate the late 1500s, and most are from the 19th or 20th centuries. Yes, including the ones you've been told are "actually medieval." They are not. O Come O Come Emmanuel is from the 19th century. Nursery rhymes and English/Scottish/Irish folk songs are also far more recent than you think, at least in terms of the definitive evidence for them.
If you don't know when your song is from, and you can't find definitive information on it to make it fit within one of these categories, pick the oldest one where there is evidence.
Do not tell me that this poll is "Western-biased" unless you have detailed knowledge of a non-Western musical tradition that has secular melodies that are still commonly-sung - and that you personally know by heart - that musicologists/ethnomusicologists know for certain predate 1000 CE. I am phrasing it this way because I am not actually unfamiliar with global musical traditions, lol.