I'd like to take a datetime string, and get the string version of its format:
e.g. 2017-01-02 would yield YYYY-MM-dd for logging purposes if a datetime is parsed incorrectly due to a parsing exception.
Is this possible with System.DateTime or any other built-in?
"2017-01-02" would yield "YYYY-MM-dd"
It's not possible. You are asking for magic, making something out of nothing.
There is no way without meta information for a computer (or a human) to decide if that is the 2nd January or the 1st February. Both is possible.
There is no reliable way of getting that format string based on a string that might look like a date.
The closest hack that I can come up with is iterating over all cultures and then trying to ParseExact the predefined DateTime patterns that are found in each culturinfo's DateTimeFormat property.
The hack would look like this:
var date = "2017-01-02";
var formats = new Dictionary<string,int>();
// go over all cultures
foreach(var ci in CultureInfo.GetCultures(CultureTypes.SpecificCultures))
{
// each culture has a DateTimeFormatInfo that holds date and time patterns
foreach(var p in typeof(DateTimeFormatInfo)
.GetProperties()
.Where(prop => prop.Name.EndsWith("Pattern")))
{
// get a pattern property from the cultureinfo DateTimeFormat
var fmt = (string) p.GetValue(ci.DateTimeFormat, null);
try
{
// try to parse the date
DateTime.ParseExact(date,fmt , ci);
// add the format
if (formats.Keys.Contains(fmt))
{
formats[fmt]++; // how often this was a valid date
}
else
{
formats.Add(fmt, 1); // first time we found it
}
}
catch
{
// no date in this culture for this format, ignore
}
}
}
// output the formats that were parsed as a date
foreach(var kv in formats)
{
// Dump is a linqPad extension, use Console.WriteLine if that bothers you
kv.Value.Dump(kv.Key);
}
and on my box this returns
yyyy-MM-dd
40
yyyy-M-d
1
Now for 01/02/2017 it would return:
dd/MM/yyyy
255
d/M/yyyy
93
M/d/yyyy
20
d/MM/yyyy
11
MM/dd/yyyy
2
which shows a bit of the concerns raised in the comments. Without knowing the culture a date string was generated it is a guess what the date format was. Worst case it was a string with numbers and dashes between them.
Related
I need only date in the yyyy-MM-dd format, but I'm getting (20/03/2018 0:00:00) date in wrong format.
var d = Convert.ToDateTime("2018-03-20T00:00:00.000",CultureInfo.InvariantCulture).ToString("yyyy-MM-dd");
var finaldate = DateTime.TryParseExact(d, "yyyy-MM-dd", null);
Output i am getting --20/03/2018 0:00:00
expected -- 2018-03-20
I will try to explain what the others meant when they wrote "DateTime has no format".
DateTime is a C# type that has properties for year, month, day, etc.
If you want to print a DateTime, you first have to convert it to a string. During this conversion, you can define the output format.
Also, if you parse a string into a DateTime, you can define the expected input format.
This is what the "Standard Date and Time Format Strings" / "Custom Date and Time Format Strings" are for.
An example:
string d = Convert.ToDateTime("2018-03-20T00:00:00.000",CultureInfo.InvariantCulture).ToString("yyyy-MM-dd");
DateTime finaldate = DateTime.TryParseExact(d, "yyyy-MM-dd", null); // not a string!
int year = finadate.Year; // year == 2018 (a number!)
int month = finaldate.Month; // month == 3 (a number again!)
string isoFormat = finaldate.ToString("yyyy-MM-dd"); // isoFormat == "2018-03-20"
string usFormat = finaldate.ToString("MM/dd/yyyy"); // usFormat == "03/20/2018"
// and so on...
Note that if you just call ToString() without specifying any format, the result will depend on the culture of the current thread (probably "en-Us" judging from the output you have shown). See DateTime.ToString Method.
DateTime always returns DateTime object with the time part.
To get expected output, you have to return string eg. DateTime.Now.ToString("dd-MM-yyyy")
I try to convert persiandate to standard date.So my persian date has these formats (it means the user can enter these formats :
1392/1/1
1392/01/01
1392/01/1
1392/1/01
So i write a function to convert my persian date to standard date like this :
public DateTime ConvertPeersianToEnglish(string persianDate)
{
string[] formats = { "yyyy/MM/dd" };
DateTime d1 = DateTime.ParseExact(persianDate, formats,
CultureInfo.CurrentCulture, DateTimeStyles.None);
PersianCalendar persian_date = new PersianCalendar();
DateTime dt = persian_date.ToDateTime(d1.Year, d1.Month, d1.Day, 0, 0, 0, 0, 0);
return dt;
}
But these function just can handle this formats 1392/01/01 and of the users enter other formats i got this error:
String was not recognized as a valid DateTime
Best regards
You're specifying MM and dd in your format, which require two digits. Just specify "yyyy/M/d" as the format - that should handle both 1 and 2-digit day/month values. (You can specify multiple formats instead, but in this case you don't need to. You might want to consider doing that just to be clear, but M and d will both handle two digit values with a leading zero with no problems.
Note that if you're just specifying a single format, you don't need to put it in an array. You can just use:
string format = "yyyy/M/d";
DateTime d1 = DateTime.ParseExact(persianDate, format,
CultureInfo.CurrentCulture,
DateTimeStyles.None);
However:
I suspect you want to specify the invariant culture, given that you don't want this value to affected by the culture
Your current approach of converting a date to the Persian calendar will simply not work.
Currently you're implicitly validating that the date given is in the Gregorian calendar, but then you're treating it as a Persian date. For example, 1392/02/30 is a valid Persian date, but not a valid Gregorian date.
Instead, you should use a culture which already uses the Persian calendar, and then specify that as the culture in your DateTime.ParseExact call. Then you don't need to do anything else afterwards.
You might alternatively want to consider using my Noda Time library - version 1.3 which includes the Persian calendar should be released in the next day or two.
Sample code using Noda Time:
var persian = CalendarSystem.GetPersianCalendar();
// The pattern takes the calendar system from the default value
var sampleDate = new LocalDate(1392, 1, 1, persian);
var pattern = LocalDatePattern.CreateWithInvariantCulture("yyyy/M/d")
.WithTemplateValue(sampleDate);
var date = pattern.Parse("1392/02/30").Value;
Console.WriteLine(LocalDatePattern.IsoPattern.Format(date));
Specify all formats in string[] formats:
string[] formats = { "yyyy/MM/dd", "yyyy/M/d", "yyyy/MM/d", "yyyy/M/dd" };
But these function just can handle this formats 1392/01/01
Because your yyyy/MM/dd format only support this value.
If your input can be
1392/1/1
1392/01/01
1392/01/1
1392/1/01
values, you should provide all formats that support these in your formats array in your DateTime.ParseExact method.
string[] formats = { "yyyy/MM/dd", "yyyy/M/dd", "yyyy/MM/d", "yyyy/M/dd" };
With these formats, if your value matches one of these formats, your parsing will be succeeded.
I need a custom regex to math short date pattern(etc. "M/dd/yyyy", "dd/mm/yyyy", "yyyy/mm/dd",...depend on culture..) then I can get day,month,year to parse that format like this:
string input = "03/24/2013";
Match m = Regex.Match(input, #"^(?<day>\d{1,2})/(?<month>\d{1,2})/(?<year>\d{4})$");
if( m.Success )
{
DateTime d = new DateTime(int.Parse(m.Groups["year"].Value),
int.Parse(m.Groups["month"].Value),
int.Parse(m.Groups["day"].Value));
}
but! this expression not support all various formats so
require :
Accept only '/' as separators.
Valid all short date pattern(Date only,also Time would be great) in various cultures (etc, en-US, th-TH, jp-JP,...). Is this possible, actually I just need to know which part is year, month or day but I couldn't find it anywhere. Please help me...
Valid common range: day [1-31]{1-2}, month [1-12]{1-2}, year[1600-9999]{4}
As Jim and I suggested, you can just iterate over all cultures:
foreach (var culture in CultureInfo.GetCultures(CultureTypes.SpecificCultures))
{
DateTime result;
if (DateTime.TryParseExact(text, "d", culture, DateTimeStyles.None,
out result))
{
// Valid - return, or whatever
}
}
Note that "d" is the standard format string for a short date pattern. Alternatively, you could use culture.DateTimeFormat.ShortDatePattern.
Is there a way, a good way, to test if a string than I want to transform in DateTime is dd/MM/yyyy or MM/dd/yyyy ?
Thanks,
No, because it could be both. Is 11/10/2010 November 10th or October 11th?
Yes, in some cases (if one number is above 12) it will be unambiguous - but I think it's better to force one format or the other. If you just treat anything which can be done as MM/dd/yyyy that way, and move on to dd/MM/yyyy if it fails (or the other way round) then you'll get some very surprised users.
If this is part of a web application or something similar, I would try to make it completely unambiguous by using month names instead of numbers where possible.
No, but you could try both when parsing:
DateTime result;
if (DateTime.TryParseExact(
"05/10/2010",
new[] { "MM/dd/yyyy", "dd/MM/yyyy" },
CultureInfo.InvariantCulture,
DateTimeStyles.None,
out result)
)
{
// successfully parsed date => use the result variable
}
This problem will exist until all accepts and uses the ISO way. I'm a Swedish programmer working a lot with American and English clients and it's surprisingly hard to get these clients to use the standardized date format.
ISO 8601 - Use it!
Take a look at DateTime.ParseExact and DateTime.TryParseExact.
string date1 = "24/12/2010";
CultureInfo provider = CultureInfo.InvariantCulture;
DateTime dt1 = new DateTime(1, 1, 1);
bool dt1Valid = false;
try
{
dt1 = DateTime.ParseExact(date1, "dd/MM/yyyy", provider);
dt1Valid = true;
}
catch
{
dt1Valid = false;
}
I have a date string in format "08/1999" I want to get the first date of the corresponding month. eg : in this case 08/01/1999.
It is simple for en-Us culture. I break the string, append "01" in the string to get 08/01/1999 and then DateTime.Parse(datestring) but this is valid for en-US culture only.
How can I do this for different culture ?
My datestring will always be in mm/yyyy format. and I am trying to obtain a DataTime obj from this dateString.
Use ParseExact method. Note upper-cased M's are for months and lower-cased m's for minutes.
string dateToConvert = "08/1999";
string format = "MM/yyyy";
CultureInfo provider = CultureInfo.InvariantCulture;
DateTime result = DateTime.ParseExact(dateToConvert, format, provider);
Output:
{1999-08-01 00:00:00}
You can also use Convert.ToDateTime and Parse methods. It will produce the same result, but in implicite way:
DateTime result = Convert.ToDateTime(dateToConvert, provider); // Output: {1999-08-01 00:00:00}
DateTime result = DateTime.Parse(dateToConvert, provider); // Output: {1999-08-01 00:00:00}
Read more at:
Parsing Date and Time Strings
Standard Date and Time Format Strings
Custom Date and Time Format Strings
I'm not sure if I understand your question correctly, but you can try passing CultureInfo.InvariantCulture if you want to force the US date format regardless of the regional settings of the client computer:
DateTime.Parse("08/1999", System.Globalization.CultureInfo.InvariantCulture)
I break the string, append "01" in the string to get 08/01/1999 and then DateTime.Parse(datestring)
That's a very long-winded way to do it. Simply this will work:
DateTime.Parse("08/1999")
How can I do this for different culture ?
If your string is always in this format, do this:
DateTime.Parse("08/1999", CultureInfo.InvariantCulture)