# File lib/numru/nusdas.rb, line 91
    def time_from_basetime(vtime, btime, unit)
      t = vtime - btime
      case unit.upcase
      when "MINUIT"
        # nothing to do
      when "HOUR"
        t /= 60
      when "DAY"
        t /= 1440 # 60*24
      else
        raise "sorry unit #{u} is not supported"
      end
      return t
    end