Looks for date strings of multiple common formats

dateChecking.swift

import Foundation

//https://nsdateformatter.com/
//https://stackoverflow.com/questions/3917250/converting-nsstring-to-nsdate-and-back-again

let testStrings = [
    "Sep 2, 2020 8:08 PM",
    "2018-09-12T14:11:54+0000",
    "done: 2018-09-12T14:11:54+0000",
    "2018-08-13 14:11:54 +0000",
    "20:32 Wed, 30 Oct 2019",
    "06.11.2020",
    "2020.12.30",
    "15 June 2020",
    "Tomorrow",
    "200831",
    "200830 16:32"
]

let datePatterns = [
    "yyyy-MM-dd'T'HH:mm:ssZ",
    "yyyy-MM-dd HH:mm:ss Z",
    "d MMM yyyy HH:mm:ss Z",
    "MMM d, yyyy h:mm a",
    "MM-dd-yyyy HH:mm",
    "HH:mm E, d MMM y",
    "yyyy.mm.dd",
    "dd.MM.yy",
    "yyMMdd",
    "yyMMdd HH:mm",
    "d MMMM yyyy"
]

func dateFromDefinedString(_ candidateString:String) -> Date? {
    let dateFormatter = DateFormatter()
    for datePattern in datePatterns {
        dateFormatter.dateFormat = datePattern
        //print("testing formatter: \(dateFormatter.string(from: Date()))")
        if let date = dateFormatter.date(from: candidateString) {
            //print("date formatter: \(dateFormatter)")
            return date
        }
    }
    return nil
}

func dateFromString(_ candidateString:String) -> Date? {
    var foundDate:Date?
    let types: NSTextCheckingResult.CheckingType = [.date]
    do {
        let detector = try NSDataDetector(types: types.rawValue)
        detector.enumerateMatches(
            in: candidateString,
            options: [],
            range: NSRange(0..<candidateString.count)) { (result, _, _) in
                foundDate = result?.date
        }
    } catch let error {
        print(error)
    }
    
    return foundDate
    
}

for s in testStrings {
    print(dateFromDefinedString(s))
}

print("---")

for s in testStrings {
    print(dateFromString(s))
}


//RESULTS
//Optional(2020-09-03 03:08:00 +0000)
//Optional(2018-09-12 14:11:54 +0000)
//nil
//Optional(2018-08-13 14:11:54 +0000)
//Optional(2019-10-31 03:32:00 +0000)
//Optional(2020-11-06 08:00:00 +0000)
//Optional(2020-01-30 08:12:00 +0000)
//Optional(2020-06-15 07:00:00 +0000)
//nil
//Optional(2020-08-31 07:00:00 +0000)
//Optional(2020-08-30 23:32:00 +0000)
//---
//Optional(2020-09-03 03:08:00 +0000)
//Optional(2018-09-12 14:11:54 +0000)
//Optional(2018-09-12 14:11:54 +0000)
//Optional(2018-08-13 14:11:54 +0000)
//Optional(2019-10-31 03:32:00 +0000)
//Optional(2020-06-11 19:00:00 +0000)
//Optional(2020-12-30 20:00:00 +0000)
//Optional(2020-06-15 19:00:00 +0000)
//Optional(2020-09-03 19:00:00 +0000)
//nil
//Optional(2020-09-02 23:32:00 +0000)