By focusing on a simple extension of Lambda cold dark matter (ΛCDM) in which the dark energy equation of state is allowed to vary, we assess which epoch(s) possibly source the H0-tension. We consider cosmic microwave background (CMB) data in three possible ways: (i) complete CMB data; (ii) excluding the low-l+lowE (l<30 temperature and polarization) likelihoods; (iii) imposing early Universe priors, which allow us to disentangle early- and late-time physics. Through a joint analysis with low-redshift supernovae type-Ia and gravitationally lensed time delay datasets, and neglecting galaxy clustering baryonic acoustic oscillation (BAO) data, we find that the inclusion of early Universe CMB priors is consistent with local estimate of H0, while excluding the low-l+lowE likelihoods mildly relaxes the tension. This is in contrast to joint analyses with the complete CMB data. Our simple implementation of contrasting the effect of different CMB priors on the H0 estimate shows that the early Universe information from the CMB data when decoupled from late-time physics could be in agreement with a higher value of H0, even for ΛCDM model with no necessary modification. We also find no evidence for the early dark energy model using only the early Universe physics within the CMB data. Finally, using the BAO data in different redshift ranges to perform inverse distance ladder analysis, we find that the early Universe modifications, while perfectly capable of alleviating the H0-tension when including the BAO galaxy clustering data, would be at odds with the Ly-α BAO data due to the difference in rd vs H0 correlation between the two BAO datasets. We therefore infer and speculate that source for the H0-tension between CMB and local estimates could possibly originate in the modeling of late-time physics within the CMB analysis. This in turn recasts the H0-tension as an effect of late-time physics in CMB, instead of the current early-time CMB vs local late-time physics perspective.
