Some people are only just realising the true meaning of the letters AM and PM - and experts have pointed out it may mean they technically aren't telling the time correctly.
While it may have once been something that everyone learned in school, with devices like our phones and laptops using the 24-hour clock the use of AM and PM has become less frequent - so much so, it seems, that many aren't even aware of what the letters stand for. When TikTok user @amayaclarke08 posed the question of what the letters mean, people were left stumped.
Several social media users took to the comments section to guess 'after midnight' and 'past midday', while others were certain the letter M stood for 'morning'. But most failed to name the correct answer - but they can perhaps be forgiven, given that the letters actually stand for Latin phrases.
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AM stands for 'ante meridiem', which translates to 'before midday' - otherwise known as the time before the sun has crossed the meridian. Meanwhile, PM stands for 'post meridiem', meaning 'after midday' - after the sun has crossed the meridian.
The meridian is an imaginary line that runs across the Earth from the North Pole to the South Pole - the Prime Meridian, which runs through Greenwich, is a line which represents 0° longitude and divides the eastern and western hemispheres, just as the equator divides north and south. Historically, every place on the planet was measured in terms of its distance east or west from this line.
According to Royal Museums Greenwich, the meaning behind AM and PM means that you may have been saying the time wrong when it comes to the twelve-hour clock. Experts at the museum explained that while people usually refer to 12 midnight as 12am and 12 noon as 12pm, this isn't technically correct.
"At exactly 12 noon, the sun is at its highest point in the sky and directly over the meridian," they explained. "It is therefore neither 'ante' (AM) nor 'post' (PM) meridiem. At 12 midnight it is also neither AM nor PM.
"To avoid any confusion (and to make sure you arrive on time), it might be best to say 12 noon or 12 midnight instead," the experts suggested. "Alternatively, you could use the 24-hour clock system, where 12:00 is noon and 00:00 (or 24:00) is midnight."
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