Any picture of time is a mathematical tool according to the positivist philosophy of science I adopt. In this, a physical theory is a mathematical model. We cannot ask if a model corresponds to reality, because we have no independent test of what reality is. All we can ask is whether the predictions of the model are confirmed by observation. Models of quantum theory use imaginary numbers, and imaginary time in a fundamental way. These models are confirmed by many observations. So imaginary time is as real as anything else in physics. I just find it difficult to imagine.