Keithley DMM7510 Calibration Manual page 134

Model DMM7510 7½ Digit Graphical Sampling Multimeter Calibration Manual
Example 1
cal.verify.date = (os.time{year=2014, month=9, day=5})
print(cal.verify.date)
Set the verify calibration date to September 5, 2014.
Verify the date. Example output:
Sep 5 2014 12:00:00.000
Example 2
cal.verify.date = os.time()
Set the calibration verification to the present date of the instrument.
Also see
cal.adjust.date
DMM7510-905-01 Rev. A / April 2015
(on page 4-11)
Section 4: TSP command reference
4-21