"Update the time stamp string(s) in the buffer.
A template in a file can be automatically updated with a new time stamp
every time you save the file. Add this line to your init file:
- (add-hook 'before-save-hook 'time-stamp)
+ (add-hook \\='before-save-hook \\='time-stamp)
or customize `before-save-hook' through Custom.
Normally the template must appear in the first 8 lines of a file and
look like one of the following: