Time is a funny thing. We all experience the passage of it, but, fundamentally it’s arbitrary. In the SI system of units, the second is defined as “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom”,
Sure. That’s helpful. To someone. Not to me.
It’s now 2018 AD. Or is that 2018 CE? Or is it 4714, or 1438, or perhaps 5778 or perhaps it’s 2010. Or perhaps it’s year 1?
We can’t agree on what year it is. But we can certainly at least agree on some semblance of the date, correct? Not really. If I’m using Julian dates, my day is going to be 12 hours off of yours.
But, since I’m writing this in the Northeastern US, let’s agree we’ll work with the Common Era Calendar and that it’s January 9th, 2018. That should work. Everything should be simple right? For many of people, it probably is. For us programmers, it isn’t.
Let’s start with a simple sentence, “Run the job at midnight on Saturday.” Can we agree on when to run it? Most of us would probably run it just as Saturday is beginning. But some would argue that it’s just as valid run it at the end of Saturday. I have in fact seen both arguments. This is where our common use of the language can fall apart. Fortunately though, we can remedy the issue. The military for example, for whom precision timing can be critical would say something like, “Run the job at 00:00 on Saturday.” Now at least we’re in agreement.
But even then, we love to muck things up. Let me start with being a pedant for a second and point out that there is technically no such thing as 12 PM or 12 AM. “What?”, you might say? “Of course there is!” Nope, sorry. Going back to the Latin PM and AM mean Post-Meridiem and Ante-Meridiem, i.e. after and before the middle of the day. So technically, what we call 12 Noon can’t be either (since it’s neither before nor after the time of the middle of the day, it IS the middle of the day). And equally, one can argue that 12 Midnight is neither. And yet, you hear folks use the terms anyway.
Almost always, but not always though 12PM is associated with Noon and 12AM with Midnight. This follows because 12:00:01 IS after the middle of the day. So it makes sense to call the second before that also PM. Yet, that said, I have seen multiple times signs claiming that a place is open for dinner from say 7:00PM-12:00PM and or open “All Day from 7:00 AM-12:00PM” and they’re clearly open after lunch and even after dinner. (And by the way, does it strike you as a strange that we count 12AM, 1AM, 2AM etc to 11AM.. and start over at 12PM, 1PM… i.e. the 12 is considered part of the next set of hours even though we immediately move back to 1 after it? It’s one reason I really prefer a 24 hour clock.)
So I get pedantic about this when folks say 12PM or 12AM and ask them to clarify. This is especially important when it comes to scheduling tasks in say SQL Server.
BUT, we have yet another problem. I’m in the Eastern Time Zone of the US. You might be in the Pacific Time Zone of the US. I want to hold a meeting at 3:00 PM. Is that my time or your time? Most modern scheduling software will correctly put this into my calendar as a 3:00 PM meeting and into yours as a 12 Noon meeting.
Yet that’s still not enough. I was recently reminded of this a few months ago as I started to schedule my PASS Summit into my calendar. I put the events in while I was in the Eastern Timezone, forgetting that when I got to Seattle, my calendar would “nicely” shift things for me 3 hours. This meant rather than say thinking I wanted to attend the 9:00 AM Summit, I wanted to attend a 6:00 AM Summit. Fortunately again, the software I discovered DOES let me specify what timezone the appointment actually is in when I set it up.
And one more aside. If we schedule a meeting at 3:00 PM (and we both agree on what that means) what happens if I say “Oh, I have a conflict, can we move that back an hour?” We we moving it backwards in time to 2:00 PM, or backwards in the sense of “further away” and mean 4:00 PM?
So, we can agree that hours are tough. But it can get worse. Here’s a question for you. When was George Washington born? My father was always proud that he shared George Washington’s Birthday. But did he? Was it February 22nd 1732? What if I told you he was born February 11th 1731? Both are technically correct (which is the best kind of correct.)
We all know about leap years. We have them because it doesn’t take exactly 365 days to orbit the sun. It takes closer to 365.25 days to orbit the sun. But even THAT isn’t really accurate enough. When Julius Caesar reformed the Roman Calendar, he added the concept of leap years. He know that without them, the calendar would slowly get out of synch with the seasons. Before you knew it, July would start becoming the middle of winter and who would want that! (Ok, technically it would take a few hundred years, but you get the point).
The problem was, scheduling Leap Years still wasn’t enough. By 1582, despite leap years, the calendar had “slipped” by 10 days. So Pope Gregory instituted the current calendar most of the world uses which added the more complex rule of leap years every 4 years, unless the year is divisible by 100 which are not leap years, except in the cases of when it’s divisible by 400 when it is a leap year.
Now, Pope Gregory had a lot of influence over parts of Europe, so predominately Catholic countries adopted the changes almost immediately, in 1582. But understandably, the more Protestant countries were a bit slower to adopt. The Great Britain and the Colonies didn’t adopt it until 1752, after George Washington’s birth. So, he was born on either day depending on which calendar you’re using. And by then things had slipped 11 days. (The change in years is a related, but different issue that had to do with what was considered the first day of the year. It wasn’t always January 1st you know.)
Now, when Y2K rolled around, I have to admit, I started to wonder, and still do, what would have happened if we had had computers in 1899. Would they have gotten the lack of a leap year correct? My guess is, “probably not”. And in fact, ironically enough, I recall at least one software package (I can’t recall the name) that is well prepared for 2100 and 2200 and 2300, but was NOT prepared for the year 2000 and in fact skipped the leap day that year. (Oh, by the way to really blow your mind, depending on the calendaring system, the leap day is actually February 24th. Or perhaps a more accurate way of saying it is that the leap day is inserted after the 53rd day of the year.)
In conclusion let’s just say time been on my mind a lot lately, partly because I’ve orbited the Sun just over 50 times now and because it’s a new Year. And as a developer, at times handling dates can be far tougher than it looks at first pass, you have to deal with midnight boundaries, timezones, leap years (or the lack of them) and even wholesale shifts in calendars (and this is ignoring completely different calendars such as the numerous lunar based ones that may or may not have entire leap months!) Oh and completely left out any mention of leap seconds! Yes, you can have December 31st 23:59:60 as a valid time.
But when you think about it, other than the fact that time keeps slippin’ (slippin’, slippin’) into the future, all measurement is really arbitrary. We pick a 0 point and go with it. We just have to agree at some point (in time, yes, the irony is not lost on me) what that 0 point is and how we’ll measure from there, and we’re all good.
Or are we? I’ll leave you with this one final thought. Far into the future, possibly trillions of years, when the Universe has expanded so much that the distance between particles is far enough that none can interact, essentially nothing will be changing. Can you even have time if you have no clock against which to measure it? Will time eventually run out?
I could go on and on about time, but, I seem to have run out of it.