The first days of post-cardiac arrest (CA) coma represent a volatile yet underexplored state, as neural functions drastically change over time. Previous literature has shown that bodily functions of patients fluctuate within a day, some of which follow circadian rhythms. The information content of electroencephalography (EEG) activity, such as Lempel-Ziv complexity (LZc) or the slope of the 1/f-power decay can differentiate between levels of consciousness, while the phase-locking value (PLV) in the first 24 h of coma is predictive of patients’ outcome. Yet, it remains unknown how these measures fluctuate over the course of days. Here we focus on a cohort of prolonged (24 - 48 h) EEG recordings in ten post-CA patients in coma. We calculate the LZc and the PLV to characterise neural synchrony and the 1/f-slope on heart peak aligned EEG epochs. Fluctuations in all measures can be observed in the EEG data over time of coma at multiple timescales, within individual hours and across days. To evaluate effects of time of recording and outcome, the data is modelled with a linear mixed effects model. For PLV, LZc and 1/f-slope we find a main effect of time and an interaction effect of time by outcome of the 1/f-slope. No main effect of outcome was found for any of the measures. Our results suggest great variations of neural responsiveness at multiple timescales and have implications on the timing of outcome prediction in coma patients.