For example: “1 hr” works “1hr” fails. Things like “an hour”, “a hour”, “one hour” or even “one hours” should work.
I think parsing needs some work here. May I suggest to take a look at todoist and draw up a set of tests from here.
From a developer perspective you don’t need AI natural language parsing neural networks outsourced to a AWS/ GCP API to handle this, break out some regex and case statements 
Thanks