As per Fj’s previous post

Regulatory Requirement:

The regulatory deadline for mailing proxy materials to security holders is at least 21 days before the Meeting Date [Required by all statutes]. If material is mailed to registered security holders using Notice and Access, National Instrument 51-102 states that the notice and proxy must be mailed a minimum of 30 days before the Meeting Date.

So, if the company is not using “notice and access”, 3 weeks notice is required.  However, it’s recommended an additional 4 days added to ensure materials are received with 3 weeks notice.

https://www.computershare.com/ca/en/eguide-planning-mailing-date