No, this is not an archaic word from Shakespeare days of yore – at least not in Australia. You don’t get paid biweekly, or even every two weeks there; you get paid fortnightly. It took a bit of thinking before I realized that fortnight is an abbreviation for “fourteen nights”, which really, makes more sense than the Canadian bi-weekly. Our version makes it sound like we’re going to get paid twice a week, which would be exciting, and would maybe even make Canadian incomes equal to Australian ones!
Nevertheless, I can’t help thinking of puffy shirts and “thee” and “thou” whenever an Australian uses this word. It isn’t restricted to describing pay periods either. If people go away for two weeks, they say they’ll be back in a fortnight. Even if I eventually move down under, I’ll never get used to it. Or I will, and my fellow Canadians will laugh at me when I use it non-ironically back home.