Found this .. should help. The 6 month rule has to do with the country.. not the last time the dog was vaccinated. Just need a letter showing your dog is up to date with shots. BTW US is not listed as a country being rabies free

so the second option is out. The rabies vaccination should be good for up to a year - although they do say specify the duration of immunity (otherwise, it will be considered valid for one year from the date of vaccination).
Steve
http://www.inspection.gc.ca/english/anima/imp/petani/canin3e.shtmlDogs may enter Canada if they are accompanied by rabies certification, which means they must have:
* a signed rabies vaccination certificate;
OR
* a signed veterinary certificate, declaring that the dog is originating from a country recognized by Canada as being rabies-free.
The rabies vaccination certificate must:
* be written in English or French;
* be issued and signed by a licensed veterinarian;
* identify the animal (as in breed, colour, and weight);
* state that the animal is vaccinated against rabies;
* indicate the date of vaccination;
* indicate the trade name and the serial number of the licensed vaccine; and
* specify the duration of immunity (otherwise, it will be considered valid for one year from the date of vaccination).
The veterinary certificate must:
* be written in English or French;
* be issued and signed by a licensed veterinarian;
* identify the animal as in breed, colour, and weight;
* state that the animal has been in the exporting country since birth or for at least six (6) months immediately preceding shipment to Canada; and
* be accompanied by documentation from a competent government authority*, stating that rabies has not occurred in the country of origin for at least six (6) months immediately preceding the animal's shipment to Canada.
*Note: a competent government authority refers to a veterinary agency or other government agency that manages a country's animal health and welfare situation, as well as handles the responsibility of veterinary certification for the purposes of international trade. The document can be either:
* a letter issued on the competent government authority's letterhead, dated, stamped, and signed by an official of the competent government authority in the country of origin; or
* a signed letter by the licensed veterinarian who issued the certificate, which must be endorsed by the competent government authority.
Additional Information
The import requirements also apply to dogs that were originally from Canada and are returning to Canada from a rabies-free country.
The import requirements also apply to dogs leaving a country that imposed quarantine, if the dog leaves before that quarantine period is completed.
Canada does not require a waiting period between the time the animal is vaccinated for rabies and the time the animal is imported into Canada.
If a dog does not meet the import requirements for rabies certification, owners will be required, at their own expense, to do the following:
* have the animal vaccinated against rabies within a specified period of time; and
* provide the vaccination record to a Canadian Food Inspection Agency office.
Related Links
* Countries recognized by Canada as rabies-free
* Frequently Asked Questions
* Inspection fees