Nearly a day? Two days? Pffffftt!!!
I spent two weeks after making a small, tiny change to a big software project. Such a tiny change that I didn't bother to back up all the other important work added to the source code. It was originally working great, just needed one tiny feature.
When it didn't work, one by one I kept deleting all the new features I added, but no mater what I removed it refused to work, even after I deleted at least a week of full-time labor on newly written & tested code.
Nothing worked, and the NY World Maker Faire deadline was only a couple of weeks away. I spent two weeks searching and deleting a third week's worth of code.
Basically, I was declaring variable storage in 8-element wide arrays, such as "array(0,1,2,3,4,5,6,7,8)". That actually leaves space for 9 variables, and I was only going to index it from "array(1) to array(8)".
No problem, the index position of 0 was not going to be used, and that's how I wrote it all.
Since there was dozens of these arrays and limited memory, I declared them as "array(0,1,2,3,4,5,6,7)" to use only 8 variable spaces.
So there I was staring at this code for several weeks and not seeing what was really right there. Well it was in different parts of the file, but it looked essentially like this:
declare int array(7);
array(1)=1;
array(2)=2;
...etc...
array(7)=7;
array(8)=8;