The Nature Astronomy paper linked by The Guardian corresponds with the arXiv version <a href="https://arxiv.org/abs/2306.04053" rel="nofollow noreferrer">https://arxiv.org/abs/2306.04053</a><p>"Whilst this time dilation has been unambiguously detected in the light curves exhibited by cosmologically distant supernovae, the appearance of time dilation in other cosmic sources [has been] less conclusive"<p>"This paper presents the detection of the cosmological dependence of the time dilation in a recent sample of almost two hundred quasars [...] in multiple wavebands over a two-decade period."<p>"In closing, we note that the lack of detection of the time dilation of quasar variability in previous studies is potentially due to the relatively small sample size in terms of the number of quasars under consideration [26], or the cadence of data sampling and characterisation of the quasar variability"<p>There is also a discussion about possibilities such as the time-evolution of quasars themselves; those possibilities are discounted.