Far from an innovative topic to be used in a film The idea of someone going from a body to another is generally linked to diabolical possession, such as in "Fallen"(Dir.: Gregory Hoblit, 1998), but how the topic is handled in "Every Day" makes it a lot different, although I need to remark that this is far from new, since it was used previously in "Cet oscur objet du désir"(Dir.: Luis Buñuel, 1977), "Palindromes" (Dir.: Todd Solondz, 2004), amd "The Imaginarium of Doctor Parnassus" (Dir.: Terry Gilliam), "I'm Not There"(Dir.: Todd Haynes) as well as "Ne te retourne pas" (Dir.: Marina de Van, these 3 shot in 2009.
The contrast is in "Sunshine" (Dir.: István Szabó, 1999), in which Ralph Fiennes performs 3 characters of a Hungarian family during 3 different historical moments.
Besides, there is a thematical resemblance in the approach to "Before I Fall" (Dir.: Ry Russo-Young, 2016). David Levithan and Laren Oliver are spreading utopical ideas and ideals here.
But I guess that the real message here is about avoiding discrimination, A considers themselves as a man and/or a woman, Add to this some details in the cast and team: Ian Alexander is a transgender person and the director Michael Sucsy and Maria Bello are homosexuals. In a scene Rhiannon is kissed by A when inside another young woman and no one is surprised, beginning with Rhiannon herself.