Forecasted temperature time period definitions

[tetraquarkneutrino]

What is time period definition for daily forecasted temperatures - Day, Night, Hi, Lo, Evening, Overnight?  What is the time period for these temperatures for a given "day"? 

For instance at my location in Michigan, the low temperature for the 24 hour period from 12am to 12am defined as that official "day" usually occurs around 6am of that "day".  Is the "Low" forecasted temperature the temperature from 6am of the 12am to 12am period defined for that official day?  Or is the "Low" forecasted temperature actually the lowest temperature from the morning of the next official "day" typically around 6am ("overnight low??").   

I have been using Weather.com so I would like to know what their definitions are but also want to know how all the major reporting channels define these.