Let X = (Xt) t≥0 be a stochastic process issued from x ∈ R that admits a marginal stationary measure ν, i.e. νPtf = νf for all t ≥ 0, where Ptf (x) = Ex[f (Xt)]. In this paper we introduce the (resp. biorthogonal) spectral projections correlation functions which are expressed in terms of projections into the eigenspaces of Pt (resp. and of its adjoint in the weighted Hilbert space L 2 (ν)). We obtain closed-form expressions involving eigenvalues, the condition number and/or the angle between the projections in the following different situations: when X = X with X = (Xt) t≥0 being a Markov process, X is the subordination of X in the sense of Bochner, and X is a non-Markovian process which is obtained by time-changing X with an inverse of a subordinator. It turns out that these spectral projections correlation functions have different expressions with respect to these classes of processes which enables to identify substantial and deep properties about their dynamics. This interesting fact can be used to design original statistical tests to make inferences, for example, about the path properties of the process (presence of jumps), distance from symmetry (self-adjoint or non-self-adjoint) and short-to-long-range dependence. To reveal the usefulness of our results, we apply them to a class of non-self-adjoint Markov semigroups studied in [28], and then time-change by subordinators and their inverses.The authors are grateful to M.Savov for discussion related to long-tailed distributions. 1 role in diverse physical applications within the field of anomalous diffusion, see e.g. [23], as well as for neuronal models for which their long range dependence feature is attractive, see e.g. [22]. We also mention that Leonenko et al. [21] and Mijena and Nane [24] investigate the orthogonal spectral projections correlation structure in the framework of Pearson diffusions, i.e. diffusions with polynomial coefficients. More specifically, in [21], the authors discuss the case when a Pearson diffusion is time-changed by an inverse of an α-stable subordinator, 0 < α < 1. Whereas the authors of [24] consider a Pearson diffusion time-changed by an inverse of a linear combination of independent α-and β-stable subordinators, 0 < α, β < 1. In this work, we start with a general Markov process that admits an invariant measure with its associated semigroup not necessarily being self-adjoint and local, and then we perform a time-change with general subordinators and their inverses.Finally, we emphasize that the notion of long-range dependence, also known as long memory, of stochastic processes has been and it is still a center of great interests in probability theory and its applications in the last decades. We refer for thorough and historical account of this concept to the recent monograph of Samorodnitsky [31]. The definitions of long-range dependence based on the second-order properties of a stationary stochastic process such as asymptotic behavior of covariances, spectral density, and variances of partial sums are among the most developed ...