Many physicists (especially experimentalists) seem puzzled by the delayed choice experiments (DCE), because, as they argue, such experiments seem to change the past. Here I discuss DCE from the point of view of (not 1, not 2, not 3, but) 7 major interpretations of quantum mechanics: 4 variants of the Copenhagen interpretation (see https://www.physicsforums.com/showthread.php?t=332269 ), statistical ensemble interpretation, many-world interpretation and Bohmian interpretation. None of these interpretations suggests that (DCE) change the past. So why so many people are puzzled by DCE? Obviously, because none of these 7 major interpretations seems acceptable to them. Or more generally, because NONE of the existing consistent interpretations of QM seems acceptable to them. 1. Shut up and calculate: You can consistently calculate the probabilities for different measurement outcomes without asking anything about deeper meaning of the numbers you obtain. Clearly, without asking such questions there is no reason to suspect that experiments might change the past. 2. Positivistic interpretation: There is no reality (or it does not make sense to talk about reality) except the measured reality. So, if you don't measure the past (which you don't in DCE), there is no reason to say that experiments may change the past. 3. Collapse interpretation: The collapse of the wave function takes place at the instant of time at which you make the measurement. Thus, in DCE, the wave ALLWAYS goes through both slits, no matter what you do after that. But, depending on your actions after the wave passing through the slits, at the instant of measurement the wave may collapse to a new wave function which differs significantly from the the wave function before the collapse. It is a radical change of the wave function, but it does not affect the past of it. 4. Information interpretation: Wave function represents your knowledge about the system. This is knowledge that allows you to predict (with non-perfect certainty) the outcomes of FUTURE experiments. At the instant of measurement your knowledge of course changes (updates), which serves to predict the outcomes of new future experiments. This knowledge is never used to predict the outcomes of the PAST experiments, unless the past experiments have actually been done and their results are recorded. In this case, these predictions on past experiments are allways compatible with the recorded data, so there is no reason to say that experiments change the past. 5. Statistical ensemble interpretation: Quantum mechanics says nothing about individual particles, but only about statistical properties of large ensembles of particles of equally prepared systems. More precisely, it says something about statistical properties for the case when they are MEASURED. So, if you don't measure the properties in the past, then QM says nothing about them. Since it says nothing about them, then, in particular, it does not say that the past properties have changed. 6. Many-world interpretation: The wave allways goes through both slits. However, due to decoherence, at the instant of measurement (and at the position of the measurement apparatus) the wave splits into many non-communicating branches, which makes the illusion of collapse as in 3. This branching does not modify the wave function in the past. 7. Bohmian interpretation: The (pilot) wave splits as in 6. The particle takes one definite trajectory ending-up in one of the branches. During its motion, the particle does not change its past. To conclude, I claim that anyone who argues that DCE affects the past must first explain why neither of the existing consistent interpretations of QM is not acceptable to him/her.