All students must pass an examination in French, German, Latin, or Greek by the end of Spring quarter of the fourth year or before the topical examination, whichever comes first. (There are special rules for students who wish to write theses in ancient Greek or Roman philosophy as well as one for those wish to write theses in German philosophy; this is detailed below.)
There are two kinds of language examinations: those administered by the Department and those administered by the University. Departmental language exams will be given twice a year and may not be taken more than twice.
Students who take the University language examination must receive a "High Pass." These are offered every quarter and there is a fee for taking them.
There is a special requirement for those working in ancient philosophy or German philosophy, since work in these fields depends heavily on one's ability to use the relevant languages.
Any student intending to write a thesis on ancient philosophy must pass the Departmental or University exam in Greek (the latter with a "High Pass"). Any student intending to write a thesis on Hellenistic or Roman philosophy must also pass the Departmental or University exam in Latin (the latter with a "High Pass"). Any student intending to write a thesis on German philosophy must pass the Departmental or University exam in German with a "High Pass".
Such students may take the Departmental exam in Greek or Latin or German a maximum of three times (as opposed to two times, which is the rule for other students).
Scheduling information and guidelines are on the wiki here.