Pennywise typically returns roughly every 27 years. The exact timing is described as a cycle that spans decades, with appearances in youth and again when the circle repeats years later, giving rise to the commonly cited 27-year cadence. However, within that broad interval, some materials note slight variations (sometimes 25 to 30 years) depending on the narrative source (novel versus film) and how the counting is framed (whether you start from the initial awakening or from when the group is adults again).

Key points to understand

• Core cadence: The creature’s awakenings occur on multi-decade intervals, most often cited as about 27 years between major appearances in Derry’s history.

• Variations exist: Some passages and analyses mention slight deviations (roughly 25–30 years), depending on whether you count from the initial encounter as children or from subsequent resurgences as adults.

• Narrative context: In Stephen King’s IT, the timing serves a storytelling mechanism that alternates between eras in which the protagonists are children and later adults, which reinforces the “cycle” motif and the sense of an ancient, cyclical menace rather than a fixed schedule.

If you’d like, I can pull precise quotes from the book and the major adaptations to illustrate how the 27-year cycle is described and interpreted across sources.