Add blog post Cosmic Drift

site/blog/cosmic-drift.md

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+---
+title: Cosmic Drift
+description: Or how I missed the school bus because of a cosmic ray.
+
+date: 2024-04-02
+
+tags:
+  - time
+  - unix-timestamps
+---
+
+So, every day I wake up at 6:55, get dressed by 7, walk to the bus stop
+by 7:13 and board the bus around 7:17. Today was different.
+
+My alarm that I have set for 6:55 rang at 7:12 and as a result, I missed the bus.
+
+> No, I didn't sleep in. There was no note in the UI saying this was a repeat alarm,
+> which there is if you snooze it or let it expire.
+
+Surely something was happening. Machines don't break whenever they want, they're
+mostly deterministic. And I doubt Samsung engineers wrote code to delay the alarm
+by 12 minutes on the date after April 1st.
+
+So, _what_ was happening? I entered the Python repl to test out a theory:
+
+```py
+>>> alarm_time = 6*60*60 + 55*60
+>>> alarm_time_real = 7*60*60 + 12*60
+>>> alarm_time_real - alarm_time
+1020
+```
+
+The total time was off by about 1020 seconds. Give or take 60, as my phone
+doesn't display the seconds of the time.
+
+> Since I'm using a Samsung SM-B310E, I assumed it uses seconds to store
+> the time. You can't even see seconds noted anywhere so I feel this is a normal
+> assumption. Even if it is false, the math still adds up for milliseconds.
+
+Wow, I thought. That's really close to 1024 (which is 2 to the power of 10).
+Maybe the 11th bit got flipped, making it increment 1024?
+
+```py
+>>> bin(alarm_time)
+'0b110000101000100'
+>>> alarm_time |= 1 << 10
+>>> bin(alarm_time)
+'0b110010101000100'
+>>> alarm_time - alarm_time_real
+-4
+```
+
+Aha! So the 11th bit got flipped by something. And that something was probably
+a cosmic ray.
+
+My main takeaway from this event is to create more than one alarm, for extra redundancy.
+Who knew being prone to sleeping in could save you from your alarm getting
+shifted 12 minutes into the future :^).