Add WIP blog post on time_t

content/blog/2023-03-09-time_t/index.md

@@ -0,0 +1,127 @@
+---
+title: The Year 2038 problem
+date: 2023-03-09
+published: false
+---
+
+In the year 2038,
+old Unix code is going to run out of bits to store time.
+This is going to be a really big problem,
+and I'm hoping I can surf it into retirement.
+
+The Y2K Bug
+===========
+
+Back in the 1990s there was this increasing panic about the
+"Y2K problem".
+These days it seems to be remembered as sort of a joke,
+like "ha ha remember how freaked out they tried to make us?
+And it wound up being a whole lot of nothing."
+A bunch of people,
+including me,
+worked their assses off to make sure nothing bad happened.
+
+The problem was that a lot of systems written in the 1960s to the 1980s
+stored the year as a 2-digit number.
+You got the full year by adding 1900 to that stored number.
+This made total sense,
+because most people were used to writing the year as,
+like, "63" or "89".
+I was taught in school to use "mm/dd/yy" format on anything needing a date.
+
+So when it became increasingly clear that "add 1900" wasn't going to work
+when the year became "00",
+a whole lot of people had to go dig through a whole lot of old programs,
+and patch them in various ways to deal with 2000 and beyond.
+
+Here are a few of the main techniques I saw,
+in order from "patching it up with chewing gum" to
+"fix that will work forever":
+
+* If the number is 60-99, add 1900. Otherwise add 2000.
+  This works only if you're storing dates after 1960,
+  and is going to stop working in 2060.
+  I guess at this point everyone involved in the 1999 fix
+  will probably be dead, so it'll be someone else's problem.
+* Alter things to store years with more than two numbers.
+  So the year 2000 is stored as 100 (1900 + 100 = 2000).
+  It's weird when you look at the raw data,
+  but it might mean you can keep using the rest of the program,
+  which means you're able to get the fix in quickly.
+* Store time as a `time_t`, which counts the number of seconds
+  since January 1, 1970 in Coordinated Universal Time (UTC).
+  I'll talk about the problem with this below.
+* Store the year as a 4-digit number,
+  which will keep working for another 8000 years,
+  and also allows you to store dates going back to the beginning
+  of most governments on Earth.
+
+When January 1, 2000 rolled around,
+there were still a couple of problems.
+I remember one payroll company was dating checks wrong,
+I think an insurance company had some sort of issue they patched pretty quickly,
+but for the most part,
+everything kept running along smoothly,
+and all the people like me who had stayed up all night in the data center
+waiting for some big emergency
+breathed a big sigh of relief and went to bed.
+
+
+The Year 2038 Problem
+=====================
+
+That third example of a fix uses the Unix `time_t`,
+which is a 32-bit signed integer.
+
+Bits?
+-----
+
+Bits are talked about a lot with computers,
+but hardly ever explained.
+Here's a really brief introduction
+based on my years of experience teaching binary to high school students.
+
+Let's start by talking about decimal, though.
+
+| # of digits | how many muffins you can count | number of different values |
+| ---- | ---- | ---- |
+| 1 | 0 - 9 | 10 |
+| 2 | 0 - 99 | 100 |
+| 3 | 0 - 999 | 1000 |
+| 4 | 0 - 9999 | 10000 |
+
+Get it?
+Now let's talk about binary:
+
+| # of bits | how many muffins you can count | number of different values |
+| ---- | ---- |
+| 1 | 0 - 1 | 2 |
+| 2 | 0 - 3 | 4 |
+| 3 | 0 - 7 | 8 |
+| 4 | 0 - 15 | 16 |
+| 5 | 0 - 31 | 32 |
+| 6 | 0 - 63 | 64 |
+| 7 | 0 - 127 | 128 |
+| 8 | 0 - 255 | 256 |
+
+See the pattern?
+Every time you add a bit,
+you get twice as many values.
+Let's extend that table:
+
+| # of bits | how many muffins you can count | number of different values |
+| ---- | ---- |
+| 1 | 0 - 1 | 2 |
+| 2 | 0 - 3 | 4 |
+| 3 | 0 - 7 | 8 |
+| 4 | 0 - 15 | 16 |
+| 5 | 0 - 31 | 32 |
+| 6 | 0 - 63 | 64 |
+| 7 | 0 - 127 | 128 |
+| 8 | 0 - 255 | 256 |
+| ⋮ | ⋮ | ⋮ | ⋮ |
+| 30 | 0 - 1073741823 | 1073741824 |
+| 31 | 0 - 2147483647 | 2147483648 |
+| 32 | 0 - 4294967297 | 4294967296 |
+
+

static/assets/css/default.css

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