Bugfix for negative results and too small results
2000-02-02 => 2001-02-01
> DATEDIF with Y unit: 0 year (returned -1 before fix)
> DATEDIF with YM unit: 11 months (returned -1 before fix)
* Merge branch 'master' of C:\Projects\PHPOffice\PHPSpreadsheet\develop with conflicts.
* First pass at moving MathTrig tests into individual test files
* Appeasement to the great goddess PHPCS
* Appeasement to the great goddess PHPCS
* Minor scrutinizer issue resolved
* More refactoring of tests into individual test files fr each math/trig function
* More work on the math/trig test refactoring, plus a bit of tidyup of date/time tests as well
* Fix test
* Fix docblock in test
* Finish refactoring Math/Trig tests into separate files
* Fix SubTotal Test
* Import additional classes for SubTotal test