n. — Social customs, slang, abbreviation for May long weekend
Victoria Day long weekend; a national statutory holiday around 24 May.
Type: 5. Frequency — This term is an abbreviation for what is usually called the Victoria Day long weekend, which is around May 24th, the birthday of the former Queen of Canada. As Chart 1 shows, May long in this meaning is almost exclusive to Canada. The term seems to have been created rather recently, at least in its written form (see the 2010 quotation for predecessor forms).
The term is not listed in COD-2.
See also: two-four May Two Four
- 2007  May long is one of the biggest party weekends of the year, and you can usually expect to see some top DJs in the clubs, but local scratch-aholics are getting a real treat this year. 
- 2010  Victoria Day 2010 Long Weekend Overview
Victoria Day is a public holiday observed across Canada on the Monday before May 25th.
In 2010, Victoria Day falls on Monday, May 24.
Victoria Day celebrates Queen Victoria's birthday (May 24th). Canada is still a member of the Commonwealth of Nations, of which the Queen is head.
Victoria Day is always on a Monday, and thus the holiday is part of a long weekend, which is commonly referred to as the Victoria Day Weekend, the May Long Weekend, the May Long, or the May Two-Four (a case of beer there is called a "two-four" and many of these are consumed over the holiday). The weekend is also called the May 24th weekend, although it does not necessarily fall on May 24th. 
- 2011  Victoria Day long weekend, May long, May two-four or May run.
Call it what you will but across the country Canadians have spent the weekend -- weather permitting -- sitting around campfires and taking care of the obligatory cottage/yard/garage maintenance on this, the first long weekend of the season. 
- 2015  News for the Dispatch must be in by Thursday at 10:00am as we have a long weekend ahead of us again. Have a safe and happy May long and call me at [xxx-xxxx] with your news items. 
Images:
Chart 1: International Domain Search, 15 May 2015