Absolute value. Both systems count time from the same epoch, or zero point.
One year before the epoch is 1 January 1BCE One year after the epoch is 31 December, 1CE.
Half a year before the epoch (-0.5 years) is June 30, 1BCE. Half a year after the epoch (0.5 years) is July 1st, 1CE. These dates occur within the first year before the epoch, and the first year after the epoch, respectively.
Absolute value. Both systems count time from the same epoch, or zero point.
One year before the epoch is 1 January 1BCE One year after the epoch is 31 December, 1CE.
Half a year before the epoch (-0.5 years) is June 30, 1BCE. Half a year after the epoch (0.5 years) is July 1st, 1CE. These dates occur within the first year before the epoch, and the first year after the epoch, respectively.