how often do you have to calibrate a stopwatch?

Calibrating a stopwatch is generally not required frequently, as most digital stopwatches maintain accuracy for long periods. However, it's advisable to check its accuracy periodically, especially if it's used in critical timing situations, such as scientific experiments or competitive sports. If you notice discrepancies in timing, recalibration may be necessary. Always refer to the manufacturer's guidelines for specific calibration recommendations.