Handle printing realtime_clock::min_time correctly

We were printing it in the future, not the past.  This was due to an
underflow in the nanoseconds -> seconds calculation.  Fix that to make
the error a lot more meaningful.

Change-Id: Ie0cd6281013f12f0362cd4acf834c167f75c308a
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/time/time.cc b/aos/time/time.cc
index 697770c..0a633ef 100644
--- a/aos/time/time.cc
+++ b/aos/time/time.cc
@@ -146,8 +146,9 @@
   std::tm tm;
   std::chrono::seconds seconds =
       now < realtime_clock::epoch()
-          ? std::chrono::duration_cast<std::chrono::seconds>(
-                now.time_since_epoch() - std::chrono::nanoseconds(999999999))
+          ? (std::chrono::duration_cast<std::chrono::seconds>(
+                 now.time_since_epoch() + std::chrono::nanoseconds(1)) -
+             std::chrono::seconds(1))
           : std::chrono::duration_cast<std::chrono::seconds>(
                 now.time_since_epoch());