All sorts of documents we write include the time – when an event starts or stops or a new service begins or a person lands at the airport or arrives at the office or an embargo ends or a march steps off or when that much-anticipated giant inflatable singing flea will be in town. So getting the time right is important. But time and again our timing is off because we’re not describing time accurately.
Often, in the United States, this happens between the second Sunday in March and the first Sunday in November, when in most of the country it’s Daylight Saving Time (note, “saving” isn’t plural). During this period it’s not, say, 2 p.m. CST but 2 p.m. CDT; that is, Central Daylight Time. Each U.S. time zone name changes to reflect circumstances. EST (Eastern Standard Time) becomes EDT (Eastern Daylight Time), etc. It’s a small but important distinction and not one limited to the United States.
Since 1996 Europe (except Iceland), where Winston Churchill once said that the idea of changing clocks provides “the opportunities for the pursuit of health and happiness among the millions of people," has also had a form of this called European Summer Time, which runs from the last Sunday in March through the last Sunday in October. In the Southern hemisphere – where summer starts in December – Daylight Saving Time more or less occurs from late October through late March.
Springing ahead or falling back, however, is not without controversy. The great Canadian writer Robertson Davies said that time change suggested “the bony, blue-fingered hand of Puritanism, eager to push people into bed earlier, and get them up earlier, to make them healthy, wealthy and wise in spite of themselves." (Yes, you read that right, he was complaining about governments encouraging their people to become “healthy, wealthy, and wise.” Now that's a curmudgeon!) Despite Davies, around 70 countries worldwide adhere to “Daylight” or “Summer” time to do just that.
So while it’s true that in casual correspondence CST is okay when you actually mean CDT, and it’s sort of a moot point when scheduling meetings online since most (probably all) systems correct for time changes in meeting requests, given the opportunity it’s always best to err on the side of accuracy and use the correct acronym. After all, time waits for no man (or, for that matter, woman).