Initiation of the Work of Herod's Temple ISBE
Herod became king de facto by the capture of Jerusalem in 37 BC. Some years later he built the fortress Antonia to the North of the temple (before 31 BC). Midway in his reign, assigning a religious motive for his purpose, he formed the project of rebuilding the temple itself on a grander scale (Josephus gives conflicting dates; in Ant, XV, xi, 1, he says "in his 18th year"; in BJ, I, xxi, 1, he names his 15th year; the latter date, as Schurer suggests (GJV4, I 369), may refer to the extensive preparations). To allay the distrust of his subjects, he undertook that the materials for the new building should be collected before the old was taken down; he likewise trained 1,000 priests to be masons and carpenters for work upon the sanctuary; 10,000 skilled workmen altogether were employed upon the task. The building was commenced in 20-19 BC. The naos, or temple proper, was finished in a year and a half, but it took 8 years to complete the courts and cloisters. The total erection occupied a much longer time (compare Jn 2:20, "Forty and six years," etc.); indeed the work was not entirely completed till 64 AD-6 years before its destruction by the Romans.Read More about Initiation of the Work of Herod's Temple ISBE