Or without using another cell try selecting the number and:0

Data|Text to columns

keep click next until you get to a screen with 'Column data format'
Select date and in the dropdown YMD
Click finish

Mike

"Lionel H" wrote:

If I type the number (that's number) 20070919 into a cell, the majority of
the english speaking world will recognise instantly that it also represents a
date. What is the quickest and easiest way of persuading Excel to do the same
thing?