If you’re ever designing a file format, please don’t spend any time trying to keep it small, otherwise people like me will end up hating you for making it so difficult to read & debug. If you want to keep the size down, try instead designing a file format that is very easy to understand with a clear, unambiguous structure, and then pump it through a fast, free compression library like zlib when loading or saving¹. It will almost certainly achieve much greater space-savings than screwing around with 5-bit mini integers, and will be much less of a headache to maintain.

UTC & Local Time

Check out this post on jujublog [including the comments] for an idea of just how insanely complicated a simple issue involving time-zone adjustment can be. I’m still not sure I get it…

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1. More specifically, you should use zlib to create gzip compatible files, since that seems to be a defacto standard for compressed file formats [eg svgz]