fix reported difference in datetime when passed in a date in the future (addresses #44)

[jf]

Addresses #44

I considered a couple of approaches, ranging from adding the current time (and then with a +1 second; good grief! just in order to be able to bump it up at the nanosecond-level to just past 24 hours) to then-dt using atTime, to maybe doing something with the cond if passed in a date; but ultimately settled on this one as the most elegant.

A couple of notes:

• ~~I must apologize for not adding in tests for this just yet; I can take a look at this in time to come (but would also be fine getting help for this)~~ DONE
• I decided to make (datetime (java.time.LocalDate/now)) equal "today" (rather than "a moment ago"); I think that makes sense