Bhadrakalpa (Sk.). Lit., “The Kalpa of the Sages”. Our present period is a Bhadra Kalpa, and the exoteric teaching makes it last 236 million years. It is “so called because 1,000 Buddhas or sages appear in the course of it”. (Sanshrit Chinese Dict.) “Four Buddhas have already appeared” it adds; but as out of the 236 millions, over 151 million years have already elapsed, it does seem a rather uneven distribution of Buddhas. This is the way exoteric or popular religions confuse everything. Esoteric philosophy teaches us that every Root- race has its chief Buddha or Reformer, who appears also in the seven sub-races as a Bodhisattva (q.v.). Gautama Sakyamuni was the fourth, and also the fifth Buddha: the fifth, because we are the fifth root-race; the fourth, as the chief Buddha in this fourth Round. The Bhadra Kalpa, or the “period of stability”, is the name of our present Round, esoterically—its duration applying, of course, only to our globe (D), the “1,000” Buddhas being thus in reality limited to but forty-nine in all.
Source: H.P.Blavatsky - The Theosophical Glossary