Today, 3331 years ago, in the year 2450 AM, the Jews started bringing their gifts, towards the building of the Mishkan in the Sinai Desert.
The following day, he told the Jews about the building of the Mishkan.
On the 12th and 13th of Tishri, the Jews brought their gifts.
On the 14th of Tishri Bezalel started working on the construction of the Mishkan, which was completed on 25 Kislev.
Source: Shmos Rabba §51