Final answer:
The first stars were created around September 10 according to the "cosmic calendar". By 400 to 500 million years after the Big Bang, the very first stars and galaxies had already formed.
Step-by-step explanation:
According to the "cosmic calendar", which compresses the time since the Big Bang into 1 year, the first stars were created around September 10. By 400 to 500 million years after the Big Bang, the very first stars and galaxies had already formed. This information is supported by the article "The First Stars in the Universe" by Larson and Bromm.