Rotation period evolution of comet 41P as a function of time to perihelion. The DCT value (black circle) is from Farnham et al. (2017). The Lowell values (green triangles) are from Knight et al. (2017). The triangle down value is from Schleicher et al. (2017). The Swift value (blue diamond) is from Bodewits et al. (2018). The error bar on the Swift observation indicates the range of possible solutions due to the uncertainty in the change of activity as a function of heliocentric distance.