" writes:
So, Sam.... What does this mean? I know that the navigation message
contains the information about the accumulated leap seconds. I even
saw the "A leap second is coming!" part of the navigation message. I
don't know if my old yellow Etrex handles this warning properly. It's
never SEEN a leap second So are there any neat experiments to do at
7PM EST New Year's Eve?

Probably depends on what receiver you have. My observations of a couple
of Garmin handhelds at the last leap second suggest that they don't do
anything at the leap second itself - they continue counting time as if
it had not happened. Thus, after midnight, the display is an additional
second slow with respect to UTC. But the displayed time is *already*
about a second late all the time, so it can't be considered a precision
time reference in any case. When the unit is turned off and back on, it
seems to incorporate the new leap second offset at that point.

On the other hand, a GPS-25 board receiver, one that provides a 1 PPS
output for more precise timing use, did handle the leap second properly.
The NMEA output counted

23:59:59
23:59:60
00:00:00

Dave