In the year 2448 from Creation (1313 BCE), Tammuz 16 was the 40th day following the Giving of the Torah at Mount Sinai, and the people of Israel wrongly expected Moses' return from the mountain (he would actually return on the following day). When their leader failed to return, they demanded from Aaron: "Make us a god that shall go before us". Hur (Moses' nephew, the son of Miriam and Caleb) tried to stop them and was killed by the mob. Aaron fashioned a calf of molten gold.
Links:
The Making of the Golden Calf (text of Exodus 32 with Rashi's commentary)
An anthology of Midrashim and Commentaries on the making of the Calf
The Day Before (on the deeper significance of Tammuz 16, from the teachings of the Lubavitcher Rebbe)
More on the Golden calf
See also "Today in Jewish History" for tomorrow, Tammuz 17.
There’s nothing that matches the joy when a lost child returns home. And you are that child.
Because your soul began within G‑d.
And she descended into this world to inhabit a body and live as though a stranger to the heavens, captive of a futile dream, journeying upon many winding and perilous roads…
Until waking up one day and realizing that none of these lead back home.
And now, every day, with every prayer of your heart, with every word of Torah upon your lips, with every mitzvah and good deed you fulfill,
You are coming home.
There can be no greater joy—above and below.