Grain returned on time interval

When using a message with a time interval like "from 26th oct until 27th oct 3pm", I'm getting the correct times (from '26-10-2018 00:00:00', to '27-10-2018 15:00:00'), but, in my opinion, wrong grain information. Both times are returning grain 'hour', but the 'from' time should be returning 'day' instead, while the 'to' grain is correct as 'hour'. The decision to use the less or more specific grain would then be on the developer using the library.

Is this the intended functionality for any reason?