Update-grub not listing latest kernel first

[John Talbut <john@dpets.demon.co.uk>]

I have just done another kernel recompile and when I ran update-grub it listed 
the previous version of the kernel first (thereby making it the default kernel 
to boot).

I give my kernels a version according to the date on which I compiled them, i.e.:
vmlinuz-2.6.21-11sep7
vmlinuz-2.6.21-18jul7

The second of these was listed first.  Is this because update-grub puts the 
kernels in descending order of version numbers, hence 18 comes higher up than 
11, rather than, as I expected, by the date and time when the file was modified.

Can someone give me a definitive answer, please?

John