But why not have nerd (scientific) time as just the number of seconds since
a base time with no year divisions.
Then have civil time as just markers on nerd time. Quote scientific time as
seconds, Ms, Gs, Ts... Lets really go whole hog SI.
Scientific time would then just require a table noting the beginnings of
years for conversion. Both could use the same base as zero. For times in
the far past, a simple conversion could be used, and only for times where
you have accurate accounting would a table be necessary. I suspect that a
simple conversion factor would be good enough for all historical times up to
the present. Does it really matter if civil time is off by a few seconds,
or even a minute?
After all we are still living with the illogical but historical months where
September should be the 7th month but is the 9th month, and some groups
still use the Julian calendar which is off by 12 days from the current
Gregorian calendar. But that just provides more opportunities to celebrate,
civil new year and Julian or Russian New Year.