year zero
n 1. (Government, Politics & Diplomacy) the beginning (1975) of the period during which Cambodia was under the control of the Khmer Rouge
2. (Government, Politics & Diplomacy) the beginning of revolutionary change
3. the beginning of any new system or regime
[C20: by analogy with Year One of the French Revolutionary calendar]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014