The 12th of march 2018 is the application date of the new standard ISO 45001:2018, that substitutes the standard OHSAS 18001:2007

OHSAS – Occupational Health and Safety Assessment Series
OHSAS, Occupational Health and Safety Assessment Series, has been developed in response to customer demand for a recognizable occupational health and safety management system standard against which their managements systems can be assessed and certified.
OHSAS 18001:2007 has been developed to be compatible with the ISO 9001:2008 (Quality) and the ISO 14001:2004 (Environment) management systems standards, in order to facilitate the integration of quality, environment and occupational health and safety management systems by organizations, should they wish to do so.