You may well know the built-in Settings > General > Keyboard > Shortcuts feature allowing for using short shortcuts to get the system entered a predefined, even long string into the current cursor position, no matter what program you're in. In this article, I present you with more advanced forms of text macroing with particular attention being paid to inserting the current date and/or time with as little effort as possible.
If you know older but, in many respects, not necessarily worse mobile operating systems like Palm OS and Symbian, you well know these systems offered dynamic(!) macroing capabilities out of the box (without third-party tools), allowing for, among other things, quickly entering the above-mentioned date/time.