K 10
svn:author
V 3
ian
K 8
svn:date
V 27
2017-07-30T19:58:31.187700Z
K 7
svn:log
V 295
Fix AM/PM mode handling.  The bits to mask off in the hours register changes
between 12/24 hour mode.  Also fix conversion between 12 and 24 hour mode.
It's not as easy as adding/subtracting 12, because the clock doesn't roll
over 11->0, it rolls over 12->1; 0 isn't a valid hour in AM/PM mode.

END