Re: Late calibration - What do I do now?
As Manix suggested I do think it would be appropriate, mainly because your process should not allow you to "forget" to calibrate an item. One thing I'm interested in however, if you did indeed forget to calibrate by the due date, was the instrument still in use?
Your system should not only ensure calibrations are done in a timely manner, but also that instruments which are due for calibration are immediately recalled from production or otherwise identified as unusable.
It shouldn't be too difficult to make this process more mistake proof, but anyhow, yes CA is appropriate with a focus on correcting your process so that items can not be simply "forgotten" and items overdue for calibration are removed from use.