How often do you have to calibrate a hand held digital stopwatch?

A handheld digital stopwatch typically does not require frequent calibration, as they are designed for accuracy and reliability. However, it's a good practice to check its accuracy periodically, especially if it has been dropped or exposed to extreme conditions. Calibration may be needed if you notice consistent time discrepancies compared to a reliable time source. Generally, manufacturers provide guidelines on calibration frequency, if necessary.