Date parsing fails with American timezones if locale isn't American

[jonlidgard]

See: https://developer.apple.com/library/archive/qa/qa1480/_index.html
My fix: (I'm UK based & parsing Barclays Bank ofx files which use the date format 20191217000000[-5:EST]

let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0) // not sure if this is required - need to test
let maybeDate = formats.reduce(nil as Date?) { result, format in