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There's an Abbrev minor mode (set it using M-x abbrev-mode) which allows automatic expansion of abbreviations. If you find that you are often typing `at this moment in time', you can easily arrange things so that typing `waffle<space>' reproduces the phrase. You can define abbreviations interactively or from a file.
If you want to create an abbreviation for a phrase of (say) 3 words, use the standard emacs numerical argument facility. E.g., typing Save our Souls C-u 3 C-x a g sos creates an abbreviation sos.
Use M-x list-abbrevs to list and M-x edit-abbrevs to edit abbreviations. Note that there are mode-specific abbreviations as well as global ones.