Computing the start of the first day's number of milliseconds since
the epoch overflows, but adding enough seconds within the day would
have brought us back inside the representable range. So, for days
before the epoch, add a negative number of milliseconds from the end
of the next day instead of a positive number of milliseconds from the
(possibly unrepresentable) start of the target day. This is another a
follow-up to commit 2b26dea51b
Change-Id: I2e0c68d7012db85dfe7da4a8a20ba95368178ed1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>