New Moon was on September 9 (at 18h Universal Time), so the Moon is barely above the horizon at sunset.
In this picture the Moon is 31 hours old, and impossibly slender.
The Jewish and Muslim calendars base their months on the presumed first visibility of the Moon. The result of this date of New Moon, 13 days before the September equinox, is that the Jewish year began at sunset of Sep. 9, and the Muslim year will begin at sunset on Sep. 11.
So the first day of the Jewish year is Sep. 10, and the first day of the Muslim year is Sep. 12.
(The Muslim date can be given a day or so differently because of what religious authorities announce about the first visibility of the Moon.)
The difference between these two calendars arises because the Jewish date is based on a calculation of the day of the New Moon nearest to the autumn equinox; the Muslim date is based on cycles of 30 years, of which 19 have 354 days and 11 have 355.
So the Muslim year is shorter than a solar year; so the date of its first day migrates backward through our calendar year. Till 2014 it was in October, and in 2020 it will move into August. 2018 is a year of cross-over, in which these two New Years almost coincide.
And this year the Moon will be full just two days after the Fall Equinox. An unequivocal Harvest Moon.