It depends on the studio.
HBO has deals with Warner, Universal and Fox and typically gets to air their new releases 10-15 months after the theatrical release of a film. Netflix currently has deals with DreamWorks Animation, Sony Pictures Animation and Relativity to air their new releases approximately 6-9 months after theatrical. In addition, Nexflix has a deal with Epix to air their content (from Paramount, Lionsgate and MGM) 6 weeks after it debuts on Epix, which is typcally 9 months after theatrical. Netflix also gets some, but not all, of the Weinstein Company's product, and typically can offer it 7-10 months after theatrical.
Currently, Disney and Sony new releases are available via Starz (and the Starz Play apps) approx 9-12 months after Theatrical and Showtime gets the few remaining CBS films, Dreamworks Theatrical (non animated) some of the Summit titles and the bulk of the Weinstein stuff, which is available on Showtime Anywhere. These are typically available 12-18 months after release.