This paper aims at justifying and formalizing the role of the diachronic approach, and its tool,the timeline, in ethnographic research with regard to the other methods that the researcher canmobilize to build a dynamic analysis of a phenomenon. This paper proposes to develop the effectiveimplementation of the timeline in two different contexts: BtoC and BtoB. We place the timeline asan analytical tool in a “diachronic” approach, for two main reasons. First, the concept stems from thelinguistic field and is dedicated to study the evolution of a language. In this sense, it can be stronglylinked to phenomenology (Merleau-Ponty, 1976) and to speech acts (Austin, 1970). It implies thatwe focus on the actors of a phenomenon, their representations of it and how these representations(and the wording they make of it) can influence the evolution of the experience in return. Second, we base our assumption on Geertz’s view about culture. The ethnography is a technique allowing to readthe culture as a text (Geertz, 1973). It is then possible to interpret and discover hidden meanings inthe text. So, the culture of an environment can be addressed as a literary text, which presents a socialsemantic, that a diachronic approach will apprehend in its evolutionary aspect.