said by cowboyro:
No they don't. A kilogram is a kilogram, whether on the Earth at the North Pole or on the bright side of the moon. Same for a meter, same for a liter.
A kilogram may be a kilogram and a liter may be a liter but the calibration of measurement instruments can drift over time due to temperature, humidity, wear, aging, corrosion, contamination, etc.
This is why physical quantity measurement equipment needs to be periodically inspected and calibrated.