Changing date to string

[sateeshampolu]

I have a date as object in my input json . I want to store it as a string in my output json.
From what I understood Jolt doesn't do any type conversations. But I am wondering whether it is possible at all?

[milosimpson]

Enhancement. There are too many variations on String timestamps, this would be a thing where users could supply their own "functions" in Modify to do this.

[ttimaizumi]

Are there any examples on the steps to add custom functions to the chain?