Many jurisdictions allow you to average previous hours worked to determine what to pay for a Statutory or Public Holiday. In the NT you can calculate the average hours of the past 4 weeks by totaling the hours and dividing by the number of days worked. In Manitoba you use 5% of the total hours worked in the past 4 weeks.
In Ontario you can also go back 4 weeks but you must use regular and vacation PAY earned in that period.
The total is then divided by 20 to determine the current Stat Pay. For more information visit the Canadian Payroll Association website or the Labour or Employment Standards in your jurisdiction.