And count Planck time instead of seconds.. it's not as impossible as it may sound. You'll need more than 128 bits but less than 256 bits even if the epoch is the Big Bang (I can't recall exactly how many bits are needed, but I did the math once, some years ago). And it'll be compatible with alien or future time systems too, in case what we call a second (currently defined by caesium-133 periods) changes.
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And count Planck time instead of seconds.. it's not as impossible as it may sound. You'll need more than 128 bits but less than 256 bits even if the epoch is the Big Bang (I can't recall exactly how many bits are needed, but I did the math once, some years ago). And it'll be compatible with alien or future time systems too, in case what we call a second (currently defined by caesium-133 periods) changes.