Recent work by John MacFarlane, Mark Richard, Peter Lasersohn, Tamina Stephenson, and others has given new life to philosophical debate about relativism. According to MacFarlane, this form of relativism is a part of a semantic theory of natural language, which is motivated by empirical evidence. I present an independently motivated non-relativist account of this evidence, which also explains the anti-relativist cases described by von Fintel and Gillies. My account is metasemantic; in particular, I claim that speaker behaviours such as retraction of previous assertions are in part constitutive of meaning, so that the content of assertions and beliefs is determined in part by facts about times after the assertion is made or the belief is formed. I show how to make sense of assertion and belief on this metasemantic picture and argue that it has a large number of other potential applications, for example to debates about conditionals, knowledge, truth, and vagueness.