The phrase means "never" and is similar to phrases like "when pigs fly".
The Kalends (also written Calends) were specific days of the Roman calendar, not of the Greek, and so the "Greek Kalends" would never occur.
Used in mathematics and logic to denote something that is known after a proof has been carried out.
In literature, refers to a story told from the beginning rather than in medias res (from the middle).
In law, refers to something being the case from the start or from the instant of the act, rather than from when the court declared it so.
In philosophy, used to denote something that can be known without empirical experience.
In everyday speech, it denotes something occurring or being known before the event.
A judicial declaration of the invalidity of a marriage ab initio is a nullity. In other contexts, often refers to beginner or training courses.
Ab initio mundi means "from the beginning of the world". Used in law to describe a decision or action that is detrimental to those it affects and was made based on hatred or anger, rather than on reason.
A very similar phrase is nemo tenetur seipsum accusare.
A common ending to ancient Roman comedies, also claimed by Suetonius in Lives of the Twelve Caesars to have been Caesar Augustus' last words.
It is not an honorary degree, but a recognition of the formal learning that earned the degree at another college. Typically used in argumentum ad hominem, a logical fallacy consisting of criticizing a person when the subject of debate is the person's ideas or argument, on the mistaken assumption that the validity of an argument is to some degree dependent on the qualities of the proponent.