It is the time of the year again and the world is changing or not changing time. Something to do with saving light during the day. It is a source of confusion, disruption and never-ending discussion about what time is better to follow.
I would like to provide a little bit of insight. This is especially for people who say ‘Why would you make such a big deal of moving an hour forward or backward?’ Particularly, dealing with time inside a computer is quite a challenge.
Consider a simple question and answer:
Q: How long is it going to take you to do this?
A: A day.
When you say ‘day’, do you mean 24 hours? Or do you mean from this moment to the same moment the next day? What’s the difference?
Due to the Earth slowing rotation around the Sun, every so often we have to add Leap Second. When that happens you see the clock going from 23:59:59 to 23:59:60 to 00:00:00.
The statement 24 hours is 86,400 seconds is correct. The statement a day has 86,400 seconds is incorrect, it is roughly 86,400 seconds + 500 µs.
If your comment is ‘Does this 500 microseconds really matter?’, remember the quote ‘Time is money’ especially when we talk about GPS, mobile networks, electricity distribution or when it comes to High Frequency Trading (HFT), where the systems have to be able to record transactions in nano-second precision. That extra 500 µs can make you millions.
And speaking of the Leap Second, one shouldn’t forget about the Leap Year which occurs every 4 years … except every 100 years, when it doesn’t … except every 400 years, when it does.
And during the Leap Year we add 1 day. Well, not exactly. Take the Romans, they doubled a day — February 24 ‘ante diem sextum Kalendas Martias’. In some countries they added an extra month during or at the end of the year, which of course doesn’t start on January 1st.
If not confusing enough, try to answer a question — How many days and seconds are between January 1st, 1900 and now? My technically savvy readers will quickly click on the MS Excel and enter this formula for days =TODAY() — DATE(1900,1,1) and for seconds =(NOW() — DATE(1900, 1, 1)) * 86400.
Do you see the problem? Since you know about Leap Second, you already know that the 2nd formula is incorrect. What about the first one? Also incorrect!
MS Excel incorrectly counts the year 1900 as a Leap Year. Why? When Microsoft was competing with Lotus 1–2–3, which also assumed that 1900 is a Leap Year, Microsoft left this error in place for backward compatibility.
And if a day or few seconds is not that important, ask the good people in Great Britain about 1752 when they lost 11 days.
But as they say, that’s ancient history and we don’t have to worry about it now. We know better. If only.
How many hours will be in this year, the year 2026? Is it =365*24 ? Well it depends where you are counting (as in, your physical location). As of November 1st, 2026, several provinces in Canada decided not to switch back from Daylight Saving Time to Standard Time. As an example, the province of British Columbia will have a permanent Pacific Time (PCT) so the correct calculation for the year 2026 will be =365*24–1, but only in British Columbia.
Unlucky for you, MS Excel is Daylight Saving time blind. And if you are building an application which needs to calculate days, hours and seconds properly for customers around the world, you are in for a treat. Nothing is set in stone and based on government whim, a decision can happen with less than 24 hours notice like in Morocco in 2013.
And in the off chance that you want to create a scheduling application to connect people around the world at the same time, let’s add timezones to the mix. To keep noon roughly synchronized with the sun above us, we have 24 standard timezones with one hour increments. But that would be too simple. Let’s add another 11 zones with 30 minutes or 45 minutes increments; and for good measure 3 extra which are extra 13 and 14 hours ahead. Why? Why not.
For the trivia lovers, France has 13 time zones and China only 1 time zone.
The recurrent pattern in all this? I think it is time to end this piece about time and try to find an answer to the timeless question — What is time? time and time again.