3 Nephi 8

We learn that -

"...the Nephites began to reckon their time from this period when the sign was given, or from the coming of Christ..."  (3 Nephi 2:8)

That being the case and we know - 

"...the people began to look with great earnestness for the sign which had been given by the prophet Samuel, the Lamanite, yea, for the time that there should be darkness for the space of three days over the face of the land."  (3 Nephi 8:3)

Which sign would be given at the death of the Savior.  And knowing that it has been revealed in modern day that the Savior's birth was on April 6th, and that - 

"...it came to pass in the thirty and fourth year, in the first month, on the fourth day of the month, there arose a great storm, such an one as never had been known in all the land."  (3 Nephi 8:5)

This would mean the Savior was crucified on April 10th.