When was Adam created?

 The Zohar (1 37a) is the source that says on Rosh HaShanna. 

 R. Judah said: ‘Cain rose up against Abel and killed him because he inherited his nature from the side of Samael, who brought death into the world. He was jealous of Abel on account of his female, as indicated by the words, “and it came to pass when they were in the field”, the word “field” signifying woman.’ On R. Hiya objecting that, according to the text, Cain was wroth because his offering was not accepted, R. Judah answered that this was a further reason. R. Judah further expounded the words, “If thou doest well, shall there not be an uplifting?” ‘The word “uplifting”,’ he said, ‘means the dignity which is due to a first-born, provided his actions warrant it. In the next clause, “If thou doest not well, sin coucheth at the door”, this dooris the door on high from which issue the chastisements for evil deeds in this world. The “sin” which couches at that door is the angel of death, who is ready to punish thee. The word “door” (petah, lit. opening) further contains an allusion to the New Year, the day of judgement, on which Adam was born.

 But that makes the first day of creation on the 25 of Elul.The Gemora Rosh HaShanna brings two views of creation Tishrei and Nisan. According to Rabbi Eliezer the first of Tishrei is the first day of creation and that means the 6th of Tishrei is when man was created.

Rosh HaShanna (10b)  Rabbi Eliezer says: In Tishrei the world was created; in Tishrei the Patriarchs were born; in Tishrei the Patriarchs died; on Passover Isaac was born; on Rosh HaShana Sarah, Rachel, and Hannah were remembered by God and conceived; on Rosh HaShana Joseph came out from prison;

So who says Rosh HaShanna is when man was created? It is argued that the reason Rosh HaShanna is the day of judgement is either because man was created or man was first judged