This repairs an error first introduced some weeks ago during an l_fp cleanup
pass and compounded by later changes. It was insidious because the effects
would not have shown until 2036, at which point interoperability between
ntpd instances built before and after the era 1 epoch would have broken.

James Browning authored Apr 17, 2017 and Gary E. Miller committed Apr 17, 2017

The units run data acquisition every five minutes, daily stats
graphing every hour and weekly stats graphing every 12 hours.

Signed-off-by: Gary E. Miller <gem@rellim.com>