#### Code Sample, a copy-pastable example if possible pandas 0.20.3  ```python import pandas as pd rng = pd.DataFrame({ "A" : pd.date_range('1/1/2011', periods=720, freq='H')}) myvar = rng["A"] < rng["A"].values[3] ``` Works.  pandas 0.21  exact same code:  I am not sure why this would fail now? Note: it might be fixed in #18188