Calibration Interval

by Arun
(India)

I have a pressure gauge initially calibrated on 20.05.2019, next calibration should be 6 months with +/-15 days i.e 20.11.2019 +/-30days.
So I calibrate it on 02.12.2019. What should be next due date? Is it 02.06.2020 or should i consider initial date as 20.05.2020.

Because the auditor pointed that the gauge is calibrated after 20.05.2019 but still within +/-15 days, if often it is calibrated after the date, the calibration will be shifted to next month every time.

Please advise