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Change DateTime Format {"MM/dd/yyyy"} to {"dd/MM/yyyy"} and time should remain same in Unity

I want to change DateTime now to the Format {"MM/dd/yyyy"} using this code.
string.Format("{0:MM:dd:yyyy}", DateTime.Now)
and saving it.
after getting saved string I get DateTime in format {"MM/dd/yyyy"} . Now I want to convert it in another format so I can Parse to DateTime. when I try to parse MM/dd/yyyy to DateTime got an error
"FormatException: String was not recognized as a valid DateTime."
Thanks in Advance.

You can rather use DateTime.ParseExact which allows you to specify the exact date format you are expeting the input to have.
For example
var now = DateTime.Now;
Debug.Log(now.ToString("dd.MM.yyyy"));
var example1 = now.ToString("MM/dd/yyyy");
Debug.Log(example1);
var readTime1 = DateTime.ParseExact(example1, "MM/dd/yyyy", CultureInfo.InvariantCulture);
Debug.Log(readTime1.ToString("dd.MM.yyyy"));
var example2 = now.ToString("dd/MM/yyyy");
Debug.Log(example2);
var readTime2 = DateTime.ParseExact(example2, "dd/MM/yyyy", CultureInfo.InvariantCulture);
Debug.Log(readTime2.ToString("dd.MM.yyyy"));
See Fiddle

The format is only relevant for display
If you save it in a C# DateTime variable, there is no "format" when saving it, this DateTime is a struct data type which is universal and not bound to any specific format
If you want to use a specific format for parsing, you can use:
// Parse date and time with custom specifier.
CultureInfo provider = CultureInfo.InvariantCulture;
dateString = "Sun 15 Jun 2008 8:30 AM -06:00";
format = "ddd dd MMM yyyy h:mm tt zzz";
DateTime myDate = DateTime.ParseExact(dateString, format, provider);
You can use CultureInfo to optimize your format for you needs
If there is a need to save it as "MM/dd/yyyy", your should save it as string
best regards

Date Parse triggers error in ASP.NET

I'm trying to parse a date string in mm/dd/yyyy to date type, but it triggers an error saying:
String was not recognized as a valid DateTime.
This is the code I'm using:
Dim mydate As Date
If filter = 4 Then
mydate = Date.ParseExact(datepart, "mm/dd/yy", System.Globalization.DateTimeFormatInfo.InvariantInfo)
End If
I don't understand what I did wrong, any help is appreciated.

You have two little errors in your format string:
DateTime mydate = DateTime.ParseExact("07/27/2016",
"MM/dd/yyyy",
System.Globalization.DateTimeFormatInfo.InvariantInfo);
Months are parsed by "MM" not "mm" (lower case is for minutes)
The four digit year is parsed by "yyyy" not "yy"

Your date format is wrong, use MM/dd/yyyy instead mm/dd/yy try below
Date.ParseExact(datepart, "MM/dd/yyyy", CultureInfo.InvariantCulture)

CultureInfo provider = CultureInfo.InvariantCulture;
// Parse date-only value with invariant culture.
string dateString = "06/15/2008";
string format = "d";
var result = DateTime.ParseExact(dateString, format, provider);

How to convert dd/mm to Mysql Datetime format in c#

I have a date string with dd/mm format like 06/03.Now i have to store this string into mysql table column with DATETIME format.
I am getting the problem as How can i add the current year generically because i don't want to hard code it.Subsequently how will i convert it into MySql DATETIME format for saving it.
Please help me .

You can use Parse method of DateTime:
DateTime dateTime = DateTime.Parse("06/03");
UPDATE
For your comment:
Also after parsing into DateTime i am getting date correct but time i
dont want to be 12:00:00 AM instead i want it to be 00:00:00.
12:00:00 AM corresponds to 00:00:00 only. You can verify that by getting Hour property which will return 0 and also TimeOfDay will too return 00:00:00.
Even if you try to parse exact date, it also creates the same format.
DateTime dateTime = DateTime.ParseExact("06/03 00:00:00", "dd/MM hh:mm:ss",
CultureInfo.InvariantCulture);
And you don't need conversion from DateTime object to SQL compliant DateTime object. You can pass the .Net object to SQL writer.

Consider the code:
C#
string s = "06/03";
System.DateTime dateNow = Convert.ToDateTime(s);
will give the output as you required
in VB.Net :
Dim s As String = "06/03"
Dim dateNow As Date = CDate(s)
MsgBox(dateNow)

You could do something like
var some_date = "06/03";
var year = DateTime.Now.Year;
var option = some_date+"/"+year;
Or use any of the string formats to bend it to your needs
More on date string format can be found on this MSDN page.
Edit:
If you want zeroes in the time, like your comment said, you can usit Rohit vats answer and do:
DateTime dateTime = DateTime.Parse("06/03");
var s1 = dateTime.ToString("MM/dd/yy 00:00:00");
// Output: 03/06/14 00:00:00
var s2 = dateTime.ToString("MM/dd/yyyy 00:00:00");
// Output: 03/06/2014 00:00:00

Read Date Value from TextBox and Convert to Month and Year

i have a text-box in a detailview and the value of the text-box is a Date but it only shows the Month and Year and it is like this:November 2013 so i want to take this value and convert like this: 20131101. So as you can see, i would like the format to be YYYYMMDD but the day should always be 01 which is the first of the month. So how can i go from this November 2013 to this 20131101? here is my code and i know i have to convert from string to date first:
string myDate = ((TextBox)DetailView1.FindControl("InputDate")).Text.ToString();

Convert it:
TextBox txtInputDate = (TextBox)DetailView1.FindControl("InputDate");
DateTime dt = DateTime.ParseExact(txtInputDate.Text, "MMMM yyyy", CultureInfo.InvariantCulture);
then convert it to string again:
txtInputDate.Text = dt.ToString("yyyyMMdd", CultureInfo.InvariantCulture);

C# is pretty good at parsing stringy dates, you could lean on the build it parsing:
string myDateString = ((TextBox)DetailView1.FindControl("InputDate")).Text.ToString();
DateTime myDate;
if (DateTime.TryParse(myDateString, out myDate)) {
// myDate now contains a proper .NET date.
}
Now you have a proper DateTime, you can output it in any format you like.

DateTime test = DateTime.Parse("November 2013");
Console.WriteLine(test.ToString("yyyyMMdd"));

Use the DateTime.ParseExact() method, like this:
var theParsedDate = DateTime.ParseExact(myDate, "MMMM yyyy",
CultureInfo.InvariantCulture);
Now you can use the parsed date however you wish, convert it to string, send it to database, etc.

How I can get the difference by time string and Datetime now?

i want to calculate a checktime to the time now and get the hours.
I have a string "time" for example...
Jun 06 2013 07:23:06
and with DateTime.Now I get the Time now. The Problem is now that i can't calculate the difference :(
I need them in my Project where I get from the License Server the time from a user and I want to show the difference to now. I want show this in hours.

You can use the Parse method of the DateTIme class to parse a string as a date and the subtract that from now.
TimeSpan diff = DateTime.Now - DateTime.Parse(dateString);
var hours = diff.Hours
The above exsmple of course requires the date to be in a specific format. You can if needed use DateTIme.ParseExact and specify a specific format yourself

You need to first convert your string to DateTime. here you have custom format so you can use DateTime.ParseExact or DateTime.TryParseExact method as below
DateTime dt;
if (DateTime.TryParseExact("Jun 06 2013 07:23:06", "MMM dd yyyy HH:mm:ss", CultureInfo.InvariantCulture,
DateTimeStyles.None, out dt))
{
// get difference
var inDays = (DateTime.Now - dt).Days;
}

You can use TimeSpan.Hours property like;
Gets the hours component of the time interval represented by the
current TimeSpan structure.
string dateString = "Jun 06 2013 07:23:06";
var differenceHours = (DateTime.Now - DateTime.Parse(dateString)).Hours;
Console.WriteLine(differenceHours);
Here a DEMO.
If you want to convert your custom formatted string to DateTime, you can use DateTime.ParseExact which need exact format matching between string and datetime.
Converts the specified string representation of a date and time to its
DateTime equivalent. The format of the string representation must
match a specified format exactly or an exception is thrown.

u may try it
DataTime diff = DateTime.Now - Convert.ToDataTime(dateString);
var hours = diff.Hours