Something that's ahistorical completely ignores or disregards the history or tradition that came before it. An ahistorical review of a movie would leave out any references to influential films and directors.
An ahistorical political outlook can be misguided or even dangerous, because it doesn't take the lessons of the past into account. People who are nostalgic about the past are often taking an ahistorical perspective, choosing not to think about advances in civil and human rights through history. The word ahistorical dates from 1950, combining a, "not," and historical, "concerning past events."