As was announced, the visa lift for Romania and Bulgaria will come into effect on December 1, 2017, but there is a phased lift to Romania and Bulgaria, such that an advanced form of electronic travel authorization will come into effect May 1 for so-called low-risk travellers from Romania and Bulgaria. These are defined as individuals who have had a Canadian visa over the past 10 years or who currently have an American visa. Those so-called low-risk travellers will be able to get an electronic travel authorization as of May 1, and then the full lift will come into effect on December 1, 2017, as previously announced.
On March 20th, 2017. See this statement in context.