We do not know the exact Day. You also have to remember that יוֹם Yom(day) is a Hebrew word that means age, a space of time, a chronicle, a literal day, and etc. It is not specified how long of a space of time was between each day of creation!!!
Approximately 6000 years ago based on biblical chronology. Yom with an ordinal is always a 24 hour period. To make it even more clear that day means day, the Bible states that the evening and the morning were the first, second, etc day.
A long time ago
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