Article one treats conversion mainly as a sociological and psychological process. What varies just as sharply between bodies is how, or whether, they ritualise the moment of joining, and the differences are informative in their own right.
The Catholic Church formalised its process for adult converts comparatively recently in its long history: the Rite of Christian Initiation of Adults, restoring an ancient catechumenate structure, was promulgated after the Second Vatican Council and became normative from the 1970s, spreading candidates' formation across an extended period marked by public stages rather than a single moment. Protestant revivalism took the opposite route toward compression rather than extension: the altar call, developed within American revivalism and carried worldwide through crusades associated with preachers such as Billy Graham, concentrates conversion into a single public, immediate response, walking forward at a specific point in a service.
Islam requires neither an extended catechumenate nor an emotional crisis: reciting the shahada, the declaration that there is no god but God and that Muhammad is his messenger, sincerely and before witnesses, is generally held to be sufficient and immediate, with no clergy required to administer it. Judaism sits at the demanding end, requiring formal study, appearance before a rabbinical court, and for men circumcision, together with immersion in a mikveh, a process that can take years and that the tradition does not encourage anyone to shorten. The variation shows that "how long conversion should take" is itself a theological claim about what conversion is, not a neutral administrative choice.