The fact that some people use the language in a vague or unspecific manner does not invalidate English's suitability as a language for writing specs.
I doubt I've ever used "tomorrow" in a spec. I'd use "next business day" or "T+1" (with the calendar defined).
In my experience, writing a spec is an iterative process, where the developers review a draft of the spec and make comments, ask questions, point out ambiguity, etc., which provides the feedback for the next version off the spec. That process loops until everyone is happy, at which point the spec (or, at least, a portion of it) is finalised and the developers start work.
I doubt I've ever used "tomorrow" in a spec. I'd use "next business day" or "T+1" (with the calendar defined).
In my experience, writing a spec is an iterative process, where the developers review a draft of the spec and make comments, ask questions, point out ambiguity, etc., which provides the feedback for the next version off the spec. That process loops until everyone is happy, at which point the spec (or, at least, a portion of it) is finalised and the developers start work.