how to parse datetime from this format?

Question

i have a different format of datetime. I get errors 'System.FormatException' when I try to parse it. how can I parse it?

    ?time
"20170620 21:22:02 EST"

?DateTime.Parse(time)
'DateTime.Parse(time)' threw an exception of type 'System.FormatException'
    Data: {System.Collections.ListDictionaryInternal}
    HResult: -2146233033
    HelpLink: null
    InnerException: null
    Message: "String was not recognized as a valid DateTime."
    Source: "mscorlib"
    StackTrace: "   at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)\r\n   at System.DateTime.Parse(String s)"
    TargetSite: {System.DateTime Parse(System.String, System.Globalization.DateTimeFormatInfo, System.Globalization.DateTimeStyles)}

None of the answers posted deal with daylight savings as the offset is hardcoded or there is a database derivation.

Possible duplicate of [Parse string to DateTime in C#](https://stackoverflow.com/questions/5366285/parse-string-to-datetime-in-c-sharp) — lebelinoz, Jun 21 '17 at 01:31
Possible duplicate of [Parse DateTime with time zone of form PST/CEST/UTC/etc](https://stackoverflow.com/questions/241789/parse-datetime-with-time-zone-of-form-pst-cest-utc-etc) — Tetsuya Yamamoto, Jun 21 '17 at 01:40
its not a duplicate as that link does not solve the day light savings offset — junkone, Jun 21 '17 at 02:24

Tetsuya Yamamoto · Answer 1 · 2017-06-21T02:01:22.217

3

EST is 5 hours behind the UTC, so using DateTime.ParseExact may fit on your need:

String time = "20170620 21:22:02 EST";

DateTime.ParseExact(time.Replace("EST", "-05:00"), "yyyyMMdd HH:mm:ss zzz", CultureInfo.InvariantCulture);

Result in UTC:

6/21/2017 2:22:02 AM

NB: Depending on IANA's data, some timezone abbreviations have different associations depending on culture, hence there is no exact method to define which timezone should be parsed instead of defining them in application context (possibly using hardcoded values).

.NET Fiddle Example

edited Jun 21 '17 at 02:01

answered Jun 21 '17 at 01:39

Tetsuya Yamamoto

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the problem with this option is that due to day light savings, EST is not always -05:00 – junkone Jun 21 '17 at 02:21
For that case, you need to use EDT (daylight-saving version). If you're using other timezones other than EST/EDT, specify them into a list first. – Tetsuya Yamamoto Jun 21 '17 at 02:24
when you hardcode the offset, then its not correct as the offset changes based on period. https://www.timeanddate.com/time/zone/canada/toronto – junkone Jun 21 '17 at 02:31
I think it's not a good idea to hardcode offset abbreviations with non-standardized period - Jon Skeet already explain it here: https://stackoverflow.com/questions/8754563/parse-string-datetime-containing-timezone-info. However using exact offset value is applicable using `DateTimeOffset` or Noda Time. – Tetsuya Yamamoto Jun 21 '17 at 02:38

score 1 · Accepted Answer · answered Jun 21 '17 at 12:51

DateTime.Parse() method doesn't recognize your current date time string, so you need to reformat it into one of the formats that this method can understand. The following snippet could be a bit overkill :-) for this problem but it can handle quite a few scenarios.

//  "20170620 21:22:02 EST" -> "wrong" format
//  "2017-06-20T21:22:02 -05:00" -> correct format
String input = "20170620 21:22:02 EST";
String temp = input;

//  Handle US time zones.
String[] timeZones = {"AST", "EST", "EDT", "CST", "CDT", "MST", "MDT", "PST", "PDT", "AKST", "AKDT", "HST", "HAST", "HADT", "SST", "SDT", "CHST"};

Int32[] utcOffsets = { -4, -5, -4, -6, -5, -7, -6, -8, -7, -9, -8, -10, -10, -9, -11, -10, 10 };

//  Correct the timezone part
for (int i = 0; i < timeZones.Length; i++)
{
    String timeZonePattern = @"\b" + timeZones[i] + @"\b";
    String timeZoneReplPattern = String.Format("{0}:00", utcOffsets[i].ToString("+00;-00"));

    temp = Regex.Replace(input, timeZonePattern, timeZoneReplPattern);
    if (temp != input)
    {
        break;
    }
}

//  Correct the date part
String datePattern = @"(?<year>[\d]{4})(?<month>[0][1-9]|[1][0-2])(?<day>[0][1-9]|[1-2][0-9]|3[0-1])\s*";
String dateReplPattern = @"${year}-${month}-${day}T";
temp = Regex.Replace(temp, datePattern, dateReplPattern);

//  Now we should have a correct date time string
DateTime dt;
try
{
    dt = DateTime.Parse(temp);
}
catch (Exception ex)
{
    Console.WriteLine(ex.Message);
}

Hope this can help.

how to parse datetime from this format?

2 Answers2