https://www.cnet.com/news/oscars-2019-how-to-stream-online-start-time-nominees-predictions/

This year the Oscars take place at the Dolby Theatre in Hollywood on Sunday, Feb. 24. The whole event starts at 5 p.m. PT. 

Of course, if you're interested in the dresses, the pre-event interviews and all the red carpet watching, you'll want to start watching at around 90 minutes before at around 3:30 p.m. PT.