What is calibration management software?
Calibration management software keeps a register of every measuring instrument, works out when each one is due, and stores the calibration record: readings as found and as left, the standards used, the lab and certificate, and who approved it. It proves to an auditor that every measurement came from a gauge fit to use.
Gauges usually live in a spreadsheet and certificates in a shared folder. Someone checks the due list when they remember. Then an auditor picks a micrometer off the bench, it is two months overdue, and nobody can say what it measured since its last calibration or whether those parts shipped.