The Astronomical New Moon is on Wednesday 20 September 2017 T 6.30am. The crescent will not be visible anywhere on this day.
The calculations for Thursday 21 September 2017 for London is as follows:-
Crescent age. 36 hours 33 minutes
Crescent altitude 7.43 degrees
Crescent elongation 18.56 degrees
Sighting is possible on this day
1st Muharram 1439AH will be on Friday 22 September 2017.