Sentence:  Over a temperature range from 25 to 200 * * f and at pressures up to 250 atm , an overload of 300 psi , applied for a period of one <WSD>day</WSD> , results in an uncertainty in the pressure of , at most , one millimeter of mercury . 
Meaning of the word marked with <WSD> tags:  time for Earth to make a complete rotation on its axis