Taking the risk to sound like a complete idiot but why cant we technically.
agree on how late it is.
call it universal time.
It might feel like weird to live during different hours but i am sure people will adapt to their local sleeping/waking/eating moments. Most of us arent following our bioclock anyway.
Or is this about needing a way to quantify a unit of time scientifically when not on earth? But then earth reference points wont work either?