Think I read somewhere that some cultures in history did calculate time in a different way than we do...in roman times there were only 10 months until they added in august and think it was june, changing the number of days in each month
Indeed -- They were trying to make sense out of nature's diurnal and seasonal cycles and modified their systems as their knowledge and experience increased. But it was still a systematized and purposeful calculation.
We still make tweaks to those calculations today (I think they added some (mili?)seconds or minutes to one single day sometime in the last year or so, just to make the math work ;-) ...
But in terms of Mr. B's 30-hour day, you have two choices:
a) Keep the Hour at 60 of today's minutes, in which case changing a Day to equal 30 hours would encompass more than a single rotation of the earth (and thus the sun's zenith in the sky would happen at a different hour every day, processing around the clock), and would require a redefinition of everything based on a Day (weeks, months, years, etc.), or
b) Break-up the cycle that we know as a "Day" into 30 shorter segments instead of the current 24. Of course, that just means the new "8 hour workday" might be equivalent to, say, a current 6-hour workday -- in which case why wouldn't we just take the easy route and mandate a shorter workday instead of trying to monkey with our concept of time?