emacs automatically insert date last edited

Question

I'm using Org Mode and I was wondering if anyone knows how i can add the date that the file was last edited within the actual file?

Answer 1

1. Timestamp in org mode
2. Emacs (version 21 or later) has time-stamp support (See Manual:Time Stamps).
3. Library header2.el has code to insert and update a date and time field in a file header. Unlike vanilla Emacs timestamps, such a time stamp need not be within the first eight lines of the file. The default timestamp format used by header2.el looks like this, but you can customize it any way you like (option ‘header-date-format’)

Link on how to use Option 2 (the simplest and most portable way IMO)