Observed minus calculated moments of the primary minima for KIC 9832227 obtained via the template fit method yielding the OC4 values (see Sect. 2). The reference period and epoch of the primary eclipse are from Socia et al. (2018): P = 0.4579515 d, EPOCH = 2 454 953.949183 BJD. The light blue line shows the exponential model of Molnar et al. (2017) reaching singularity in 2022.2 (at HJD−2 455 000.0 = 4651). Shown is the best-fit parabola, assuming only a linear period decrease (magenta line). Data associated with certain surveys are highlighted; see Table 1 for the full dataset.