The Astronomical New Moon is on Monday 18 December 2017 at 6.30 am. The crescent is not visible on this day.
The calculations for Tuesday 19 December 2017 for London are as follows
Moon age. 33 hours 24 minutes
Moon lag time 1 hour 2 minutes
Crescent altitude 9.06 degrees
Crescent elongation 15.17 degrees
The crescent will be easily visible to the naked eye
01 Rabi ul Akhar 1439 AH will be on Wednesday 20 December 2017