Overtime is the amount of time someone works beyond normal working hours. The term is also used for the pay received for this time (https://en.wikipedia.org/wiki/Overtime). Actual hours and rates may vary from province to province in Canada, but it seems overall that this does not apply to managers and supervisors.
As outlined by the ON Ministry of Labour, “Managers and supervisors are not covered by overtime rules.”
However, to be exempt from overtime regulations, “he or she must do work that is supervisory or managerial in nature and only do non-managerial or non-supervisory work on an irregular or exceptional basis.” (https://www.labour.gov.on.ca/english/es/tools/esworkbook/overtime.php)
If this work non-managerial role becomes regular in nature, he or she “would be entitled to overtime pay if he or she works more than 44 hours in a week. Possibly employers treat this in a kind of gray area.
As a matter of interest, in the early 2000s, the Superior Court and the Court of Appeal of Quebec rejected a suit for overtime based on the fact that although the employee’s title had been reduced from Director to Analyst, his duties remained essentially managerial in nature. (https://www.lexology.com/library/detail.aspx?g=f465c103-b43e-4400-b43d-c0495706b7ac).
It is the actual duties one performs that determines who is overtime- eligible.
“Some employees have jobs where they are required to do more than one kind of work. Some of the work might be specifically exempt from overtime pay, while other parts might be covered. If at least 50 per cent of the hours the employee works is in a job category that is covered, the employee qualifies for overtime pay” (https://www.ontario.ca/document/your-guide-employment-standards-act-0/overtime-pay).
You can read further on overtime laws in Canada on the following monster.ca site (https://www.monster.ca/career-advice/article/overtime-laws-in-canada).