Hi I have 3 cells E1,F1,G11

I want to store cell IDs containing dates in E1 and F1. Cell G1 will show the number of days difference.

EG:

E1 = '06/04/2017 19:00:00'
F1 = '28/04/2017 19:00:00'
G1 = '22 Days'

I tried entering =DATEDIF(F1,E1,"D") into cell G1 but it doesn't work.