The Kitáb-i-Aqdas
Notes
62.Whoso layeth claim to a Revelation direct from God, ere the expiration of a full thousand years   ¶37
The Dispensation of Bahá’u’lláh will last until the coming of the next Manifestation of God, Whose advent will not take place before at least “a full thousand years” will have elapsed. Bahá’u’lláh cautions against ascribing to “this verse” anything other than its “obvious meaning,” and in one of His Tablets, He specifies that “each year” of this thousand year period consists of “twelve months according to the Qur’án, and of nineteen months of nineteen days each, according to the Bayán.”1
The intimation of His Revelation to Bahá’u’lláh in the Siyáh-Chál of Ṭihrán, in October 1852, marks the birth of His Prophetic Mission and hence the commencement of the one thousand years or more that must elapse before the appearance of the next Manifestation of God.
 
1 Shoghi Effendi, The World Order of Bahá’u’lláh, p. 132