How much time passed from 1st line of code till 1st revenue?

Well, this is a broad question. For solo programmers like me, projects may change with a higher frequency. I may start a project, delete it and start another based on that one. Where should I draw the "first line of code" here? Is my current project an extension of the last that failed? The same problem as the ship of Theseus. Sometimes I have to learn a new language, for example. Does this time of learning counts? Many other variables may be taken into account for a bigger analysis: size of the project, its impact, your network...