Cycle times vs. rotation period (both in days) for early M stars (rhombic symbols). Among the group of rapid rotators with rotation periods less than a day (Vida et al. 2014) are also the early M dwarfs EY Dra and V405 And (Vida et al. 2013). The remaining data are from Suárez Mascareño et al. (2016); Wargelin et al. (2017), and Distefano et al. (2017). For GJ476 the cycle time is known but not the rotation period (blue bar). The Schwabe cycle of the Sun is indicated as an asterisk denoted SUN.