Encountered two full labels using ticklabelmode: 'period'

[archmoj]

testing this out this seems to introduce a (much more minor) bug with regular non-reversed axes when the tick corresponding to the first tick label is just out-of-range, we get the full 2-line label twice:

It'd be nice to include jasmine tests for ^^ both forward and reversed, with the original range shifted in something like 6-hour increments - so ranges:

['2019-12-29', '2020-01-04']
['2019-12-29 06', '2020-01-04 06']
['2019-12-29 12', '2020-01-04 12']
['2019-12-29 18', '2020-01-04 18']
['2020-01-04 18', '2019-12-29 18']
['2020-01-04 12', '2019-12-29 12']
['2020-01-04 06', '2019-12-29 06']
['2020-01-04', '2019-12-29']

And just check that the tick text we get in each case is as expected. Something like that should cover all the related cases, I'd think.

Originally posted by @alexcjohnson in #5060 (comment)

[archmoj]

Fixed by 9399031.