There has been significant discussion about this in the past on the mailing list.
There were indeed people who liked using :<, := and :> as comparison results, but in the end the core team decided against it.
As for the helper functions you propose: DateTime was included into Elixir’s standard library mainly to have a single datatype that the different date/time-libraries would agree on, rather than each library ending up with its own incompatible types.
This means that only the bare minimum is part of Elixir itself, and all bells and whistles are (only) provided by libraries. Timex is probably the most well-known library that has most of the features you’re talking about, as @al2o3cr already mentioned.
