[dateutils] add support

Sanity checks

• My issue relates to a specific CLI completion spec (e.g. git checkout is missing options in git completion spec). If your issue is more general, please create your issue here: withfig/fig
• I have searched github.com/withfig/autocomplete/issues and there are no duplicates of my issue
• I would like to work on this.

What CLI tool does this relate to?

dateutils

Which statement makes the most sense?

This completion spec does not exist

Issue Details

Dateutils are a bunch of tools that revolve around fiddling with dates and times in the command line with a strong focus on use cases that arise when dealing with large amounts of financial data.

strptime Command line version of the C function
dateadd Add durations to dates or times
dateconv Convert dates or times between calendars
datediff Compute durations between dates or times
dategrep Grep dates or times in input streams
dateround Round dates or times to “fuller” values
dateseq Generate sequences of dates or times
datesort Sort chronologically.
datetest Compare dates or times
datezone Convert date/times to timezones in bulk

http://www.fresse.org/dateutils/