[D8] Date fields: Support both future/past dates at the same time with the "time ago" formatter

Here's what the settings for this formatter look like in Backdrop:

...and here are the available options for the "Display" setting:

...and here's the summary of the settings:

This seems very limiting, since: - The option is called "time ago", but it also allows setting it to a "time hence" - it would be better called something like "time difference" instead - You can only set the formatter to "time ago" or "time hence", which works fine if you know for sure that the field will be used to enter dates either in the past or in the future, but not both. So if you set a date in the future, the time diff will be shown as "time hence" ...but once that date comes and passes and is in the past, it will not work.

In D8+, you are allowed to set a format for both ago/hence: ...and the summary indicates that things will work for both future/past dates: