[REF] Fix Test fails on import by ensuring that Month Abbreviations a…

[seamuslee001]

…re formatted based on the first of each month

Overview

This fixes an issue where by strtotime by default will use the current day which means that the wrong abbreviation for September will show if the tests run on 31 July for example

Before

Import Date validation Test fails when run on 31 July

After

Import Date test passes no matter what date the test is run on

ping @demeritcowboy @eileenmcnaughton

[civibot]

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[demeritcowboy]

Interesting.
For this fix, I'm not sure how strtotime decides how to parse things that can be written differently in different locales (e.g. here we would write it "January 1") but it seems to get it right either way, so 👍. If we wanted to be super-sure we could switch to using mktime().