  Within ordinary ---unitary--- quantum mechanics there exist global protocols
that allow to verify that no definite event ---an outcome to which a
probability can be associated--- occurs. Instead, states that start in a
coherent superposition over possible outcomes always remain as a superposition.
We show that, when taking into account fundamental errors in measuring length
and time intervals, that have been put forward as a consequence of a
conjunction of quantum mechanical and general relativity arguments, there are
instances in which such global protocols no longer allow to distinguish whether
the state is in a superposition or not. All predictions become identical as if
one of the outcomes occurs, with probability determined by the state. We use
this as a criteria to define events, as put forward in the Montevideo
Interpretation of Quantum Mechanics. We analyze in detail the occurrence of
events in the paradigmatic case of a particle in a superposition of two
different locations. We argue that our approach provides a consistent (C)
single-world (S) picture of the universe, thus allowing an economical way out
of the limitations imposed by a recent theorem by Frauchiger and Renner showing
that having a self-consistent single-world description of the universe is
incompatible with quantum theory. In fact, the main observation of this paper
may be stated as follows: If quantum mechanics is extended to include
gravitational effects to a QG theory, then QG, S, and C are satisfied.
