What builds go to snapshots?

[Sergey Manucharian]

Excerpts from Allan Jude's message from Sun 22-May-16 23:55:
> On 2016-05-22 23:33, Sergey Manucharian wrote:
> > Is there any materialistic definition of those builds, which
> > become snapshots at [0]?
> > 
> > - Sergey
> > 
> > [0] ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/ISO-IMAGES/11.0/
> > 
> The snapshots are built with the scripts/makefiles in the 'release'
> subdirectory of the source tree.
 
Thanks, Alan! But how is it determined/decided which particular build
goes to "snapshots"? E.g. the latest builds are of May 18, why not of
May 15 or 16?

S.