Ah; I was thinking the complaint was that they do not provide instantaneous ages in days, not that they don't just give timestamps, so I was giving justifications for having the ages be reported in terms of a fixed timepoint rather than as of the moment -M, etc. is executed, even though it results in oddities such as negative ages for timestamps later than $^T.

bonus points for pointing out missing or extra commas in the above ramble; commas are not my forte