Examiners issue medical certificates under Part 67 now. Pilot licencing still operates under the old ANRs.
Part 67 states
Period of validity of medical certificates
67.00.6 (1) A Class 1 medical certificate shall be issued for a period not exceeding –[list=a][*]12 calendar months, calculated from the last day of the calendar month in which the medical certificate is issued, where the applicant is less than 40 years of age on the date on which the medical certificate is issued; and
[*]six calendar months in the case of an airline transport pilot: aeroplane and helicopter, a commercial pilot: aeroplane and helicopter, a commercial microlight aeroplane pilot, a gyroplane pilot for commercial purposes, a commercial glider pilot, an airship pilot for commercial purposes, a free balloon pilot for commercial purposes or a powered paraglider pilot for commercial purposes, calculated from the last day of the calendar month in which the medical certificate is issued, where the applicant is 40 years of age or more on the date on which the medical certificate is issued: Provided that a medical certificate may be issued for a period of 12 months to an applicant who is less than 60 years of age on the date on which the medical certificate is issued if –
(i) the applicant has no identified medical condition or excessive risk factors for conditions leading to sudden incapacity; and
(ii) the medical certificate is, for the latter six months of the period, endorsed with a special limitation referred to in subregulation (4)(b).[/list=a]
As I see it your previous medical certificate has no bearing on the issue. Your medical is valid for 12 (or 6) months from the last day of the month of issue.
[This message has been edited by Wiz (edited 25 August 2000).]