Sagittarius runs from November 22 to December 21, the ninth sign of the zodiac and the last of the fire signs, closing out autumn on the way into winter in the Northern Hemisphere. It's a mutable fire sign, which sounds like a contradiction until you watch one in action: the drive of fire aimed not at a single fixed target but at whatever new question shows up next. Where cardinal fire (Aries) starts things and fixed fire (Leo) holds a stage, mutable fire keeps moving toward the next horizon.
Jupiter rules the sign, and the planet's reputation for expansion, luck and excess shows up almost literally in Sagittarius behavior: bigger plans, bigger opinions, a default assumption that things will work out. That optimism comes paired with bluntness. Sagittarius tends to say the true thing before checking whether the room wants to hear it, which reads as refreshing from a friend and occasionally brutal from a coworker.
The archetype is the philosopher-traveler rather than the settler. Higher learning, long trips, religion, foreign cultures, anything that stretches the map or the mind, tends to pull Sagittarius in. What it resists is the fine print: the sign is better at the big idea than the follow-up email, and the gap between the two is where most Sagittarius friction actually lives.