Some unions/companies are now offering paid or unpaid religious holidays to accommodate our multicultural society. Some offer a number of days annually, like sick days, that you don't have to account for (so presumably atheists and agnostics could take time off to celebrate their views). Other employers will be open to individual arrangements with their employees.
Here's a reference to a court decision that indicates that employers must pay attention to the new realities. http://www.chrc-ccdp.ca/publications/1997_lr/page2-en.asp
(...)
In a split decision, the Federal Court of Appeal held that while the policy
of providing paid leave for Christian holidays and not for other religious
holidays was discriminatory, the options to make up the loss of pay constituted
reasonable accommodation.