The Children of Israel began building the "Mishkan" (also called the "Tabernacle"--a portable sanctuary to house the Divine presence in their midst as they journeyed through the desert) on the 11th of Tishrei of the year 2449 from creation (1312 BCE) -- six months after their Exodus from Egypt, three months after the revelation at Sinai, and 80 days after their worship of the Golden Calf. The construction of the Mishkan, which followed a detailed set of instructions issued to Moses on Mount Sinai, lasted 74 days, and was completed on the 25th of Kislev; but the Divine command to erect the edifice came only three months later, on the 23rd of Adar, when Moses was instructed to begin a 7-day "training period." During the week of Adar 23-29, the Mishkan was erected each morning and dismantled each evening; Moses served as the High Priest and initiated Aaron and his four sons into the priesthood. Then, on the "eighth day" -- the 1st of Nissan -- the Mishkan was "permanently" assembled (that is, put up to stand until the Divine command would come to journey on), Aaron and his sons assumed the priesthood, and the divine presence came to dwell in the Mishkan. Links:
Parshah Terumah (detailed description of Mishkan with commentary)
Why It's Frustrating Having a Brain
More on the Mishkan | 
