WEBVTT Kind: captions Language: en 1 00:00:00.130 --> 00:00:04.050 As I publish this video, it is already the first day of 2020. 2 00:00:04.050 --> 00:00:06.080 And it's also December 30, 2019, they haven't actually started 3 00:00:06.080 --> 00:00:08.320 rigging the fireworks on the London Eye yet. 4 00:00:08.320 --> 00:00:10.260 But the reason I can say that it's 2020 5 00:00:10.260 --> 00:00:12.520 is also the reason why, a few years back, 6 00:00:12.520 --> 00:00:14.260 Twitter failed for a few hours. 7 00:00:14.270 --> 00:00:16.660 See, there are a lot of calendars in the world. 8 00:00:16.660 --> 00:00:21.199 Yes, most of us have standardised on the Gregorian calendar, January to December, 9 00:00:21.199 --> 00:00:24.300 but there are still some used for specific things. 10 00:00:24.300 --> 00:00:26.460 In the Islamic calendar, it's the year 1441. 11 00:00:26.460 --> 00:00:28.149 In the Hebrew calendar, 5780. 12 00:00:28.149 --> 00:00:30.179 And in the ISO Week System, 13 00:00:30.179 --> 00:00:34.310 defined by the International Standards Organisation and used for finance and business, 14 00:00:34.310 --> 00:00:37.300 it is already 2020. 15 00:00:37.300 --> 00:00:40.220 It's handy sometimes, particularly when you're dealing with money, 16 00:00:40.220 --> 00:00:43.710 to always have a whole number of weeks in a year. 17 00:00:43.710 --> 00:00:47.940 And 7 days in a week just doesn't divide into 365 days in a year cleanly. 18 00:00:47.940 --> 00:00:49.860 Or 366 for a leap year. 19 00:00:49.860 --> 00:00:52.380 So back in the seventies, the ISO defined the ISO Week System: 20 00:00:52.380 --> 00:00:54.800 where the year always starts on a Monday, 21 00:00:54.800 --> 00:00:57.950 and there are always a whole number of weeks in the year. 22 00:00:57.950 --> 00:01:01.350 Most of a time that's 52 weeks, so 52 times 7: 364 days, 23 00:01:01.350 --> 00:01:04.580 but occasionally there's basically a 'leap week' to catch things up. 24 00:01:04.580 --> 00:01:08.170 Most of the time, the ISO year number is the same as the regular one we all use. 25 00:01:08.170 --> 00:01:11.719 But around New Year, it's not always in perfect sync. 26 00:01:11.719 --> 00:01:12.719 Like right now. 27 00:01:12.719 --> 00:01:15.590 As I publish this, it is December 30th, 2019, Gregorian Calendar. 28 00:01:15.590 --> 00:01:16.939 But in the ISO Week System, 29 00:01:16.940 --> 00:01:19.860 it is year 2020, week 1, day 1. 30 00:01:19.860 --> 00:01:22.060 It's a perfectly valid calendar, 31 00:01:22.070 --> 00:01:25.320 but it can be confusing because it's so close to our regular Gregorian calendar. 32 00:01:25.320 --> 00:01:29.170 And it doesn't have the concept of months. Only weeks. 33 00:01:29.170 --> 00:01:32.939 It's only meant to be used for things like bookkeeping and paying salary. 34 00:01:32.939 --> 00:01:36.140 But back at the end of 2014, Twitter's Android app and web site 35 00:01:36.140 --> 00:01:38.560 mysteriously failed for a few hours. 36 00:01:38.560 --> 00:01:42.770 And the reason was almost certainly someone getting the two calendars mixed up. 37 00:01:42.770 --> 00:01:46.080 See, most high-level programming languages have a function for getting 38 00:01:46.080 --> 00:01:50.120 the current date and time, and formatting it in a particular human-friendly way. 39 00:01:50.120 --> 00:01:53.020 So if you want the day, month and year in a human-friendly format, 40 00:01:53.020 --> 00:01:56.320 you create a string like that, you run it through a standard function, 41 00:01:56.320 --> 00:01:59.159 and it swaps out the bits that flagged by percent signs, 42 00:01:59.159 --> 00:02:01.819 and you get a sensible result out. 43 00:02:01.819 --> 00:02:05.189 But it's easy to get the letters in that string wrong. 44 00:02:05.189 --> 00:02:09.090 %m is month as a number. But %b is the month written out as a word. 45 00:02:09.090 --> 00:02:11.480 They're not always the letters you expect. 46 00:02:11.480 --> 00:02:14.840 Plus, most programmers don't have to use that often, 47 00:02:14.840 --> 00:02:18.050 so we tend to refer to the help files every time to be safe. 48 00:02:18.050 --> 00:02:22.010 And if you just search those help files from the top down for "year", 49 00:02:22.010 --> 00:02:24.500 the first result is %g. 50 00:02:24.500 --> 00:02:26.630 So you go ahead, not knowing what ISO week means, 51 00:02:26.630 --> 00:02:29.130 you use %g, and it looks right, 52 00:02:29.130 --> 00:02:32.040 and you don't realise until, well, today, 53 00:02:32.040 --> 00:02:34.890 that it's using a completely different calendar. 54 00:02:34.890 --> 00:02:39.190 And that's almost certainly why, for a few hours back at the end of 2014, 55 00:02:39.190 --> 00:02:40.820 at least, our 2014, 56 00:02:40.820 --> 00:02:41.910 Twitter got the year wrong. 57 00:02:41.910 --> 00:02:45.590 They'd accidentally taken the day and month from the Gregorian calendar, 58 00:02:45.590 --> 00:02:47.660 but the year from the ISO week system. 59 00:02:47.660 --> 00:02:50.360 It's one of those bugs that even with a lot of testing, 60 00:02:50.360 --> 00:02:53.290 you might not actually spot until something goes wrong. 61 00:02:53.290 --> 00:02:58.070 So if 2019 has been a rough year for you, and you want to leave it behind: 62 00:02:58.070 --> 00:03:00.540 change calendars for a little while. 63 00:03:00.540 --> 00:03:01.840 Welcome to the twenties. 64 00:03:01.840 --> 00:03:05.050 Fasthosts are a British web host who've been in the business for twenty years 65 00:03:05.050 --> 00:03:07.170 and host more than a million domains. 66 00:03:07.170 --> 00:03:09.250 They're offering viewers from the UK the chance to win a trip 67 00:03:09.250 --> 00:03:14.900 to SXSW 2020 in Austin, Texas, including flights and accomodation. 68 00:03:14.900 --> 00:03:19.030 To enter the draw, you need to answer this techie-test question that I've written: 69 00:03:19.030 --> 00:03:21.840 this JavaScript code is meant to simulate a coin flip, 70 00:03:21.840 --> 00:03:23.610 but it's not working properly. 71 00:03:23.610 --> 00:03:24.780 Where's the bug? 72 00:03:24.780 --> 00:03:27.920 There's one big error that means it's only returning heads. 73 00:03:27.920 --> 00:03:28.920 If you reckon you know, 74 00:03:28.920 --> 00:03:32.600 click the link in the description and you could be off to SXSW. 75 00:03:32.600 --> 00:03:36.020 All the terms and conditions are over on Fasthosts' web site. 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