fmtlib/fmt ? reverse-engineered prompt

Build me a modern C++ formatting library like fmt that makes it easy to print and build strings safely and fast.

I want a clean, easy to use API for formatting text, numbers, dates, times, containers, and custom types, with a printf style option too. It should catch bad format strings early when possible, support Unicode, work across platforms, and have good performance compared with iostreams and old style printf. Please include examples for formatting a string, printing to stdout, formatting chrono values, ranges like vectors, and writing output to a file. If it makes sense, keep it small and simple to use as a header only library option, with solid tests and clear documentation. Feel free to look up current docs online if you need to.