Use this template to sign somebody's talk post for them. This is most often needed with anonymous editors, who almost never sign. The template accepts two arguments: a required username (or IP address) and an optional timestamp, which can be copied/pasted from the edit history of the talk page. The following two examples...
...will render this way:
The timestamp of course will be rendered in whatever timezone you have set your preferences to show you, so you might want to label it. Or not. Whatever.