The story timelines largely predate the availability of cell phones, but Rowling was quite specific about when it is set, with exact dates mentioned for key poi

The story timelines largely predate the availability of cell phones, but Rowling was quite specific about when it is set, with exact dates mentioned for key points in the story: https://harrypotter.fandom.com/wiki/Dating_conventions https://harrypotter.fandom.com/wiki/Dating_conventions