Today’s concept of time traces back to Albert Einstein’s theories of special (SR) and general relativity (GR). In SR, uniformly moving clocks are slow with respect to my clocks. In GR, clocks in a more curved spacetime are slow with respect to my clocks. Many physicists anticipate that GR has an issue as it isn’t compatible with quantum mechanics. Here we show: There is indeed an issue in Einstein’s concept of time, which takes the proper time of one observer as the fourth coordinate of all objects in the universe. “Einstein time” runs into a problem if there is a unique 4D vector “flow of time” for each object. We claim that there is such a vector and that it must be rotated in 4D when transforming coordinates. SR and GR are approximations because that vector is approximately the same only for objects on and close to Earth. It is different for objects far away from Earth. We replace Einstein time with Euclidean time, which takes the proper time of an object as its fourth coordinate. We prove: The Lorentz factor is recovered in Euclidean relativity (ER); acceleration and gravitation relate to a 4D rotation; ER is compatible with quantum mechanics! We solve 13 mysteries of physics, such as mc², gravitation, the Hubble constant, the wave–particle duality, and quantum entanglement. Cosmic inflation, expansion of space, dark energy, and non-locality are redundant concepts. Therefore, Occam’s razor knocks out Einstein time.