Rabies Vaccination Requirements (Canada to Mexico)

I am travelling to Mexico with my dog mid December and we will be there until mid January. His rabies vaccination expires Jan 1st. Does anyone know how far in advance he will need to get his booster shot? I read somewhere that if it is their first shot, it needs to be at least 1 month before the travel date, but if it's their booster, it does not matter how far in advance they get it.

I contacted the CFIA but they just referred me to a link that doesn't answer my question.

Thanks for your help!