When was Zachariah serving in the Temple of Jerusalem?
Gabriel came to the Temple when Zachariah was serving on 15th of Tishri 3756 Hebrew calendar or September 26, 6 BC Julian Calendar.
Ancient Hebrew day began at sunset until next sunset. Meanwhile, sunset time is about 6 pm. In September 5, 6 BC Julian Calendar, sun set at 5.33 pm according to Millenia Calendar software. Thus, 15th of Tishri 3756 took place from September 24, 6 BC ± 6 pm to September 25, 6 BC 05:33 pm.