If this is to be taken at face value: "TOML aims to be a minimal configuration file format", then embedding all of RFC 3339 to get datetime literals makes no sense. Since the string values of TOML keys are restricted, I don't see TOML as being appropriate as a general data serialization protocol (in which a native datetime literal would be useful), so I assume it really is meant to be for human-edited config files. I've written/edited plenty of configuration files, and I can't remember when I ever needed to encode a datetime by hand.