DateTime.ToString

When you want to format a date you have two choices.
(1) Use a built-in standard date format
(2) Use a custom date format

To format a date tou can use the ToString method

System.DateTime oDateTime; 
oDateTime = System.DateTime.UtcNow; 
System.Diagnostics.Debug.Print(oDateTime.ToString("dd-mm-yyyy"));

Instead of always using a custom date format there are also some built-in standard formats
These standard formats are only one character long.
If the format provided has more than one character it is assumed to be a custom format.

System.Diagnostics.Debug.Print(oDateTime.ToString("d"));

d	Short Date
D	Long Date
f	Full Date (Long Date Short Date)
F	Full Date (Long Date Long Time)
g	General Date (Short Date, Short Time)
G	General Date (Short Date, Long Time)
m, M	Month Day
o, O
r, R
s
t	Short Time
T	Long Time
u	Universal (Short Date Short Time)
U	Universal (Long Date Long Time)
y, Y

System.Diagnostics.Debug.Print(oDateTime.ToString("d", new CultureInfo.CurrentCulture)); 
System.Diagnostics.Debug.Print(oDateTime.ToString("d", new CultureInfo("en-US")); 
System.Diagnostics.Debug.Print(oDateTime.ToString("d", new CultureInfo("en-GB"));

The easiest way to obtain a date/time in a a specific format is to use the ToString method

oDateTime.ToString("dddd, dd mmm yy") = "Monday, 18 Jul 06"

oDateTime.ToString("m") = ??

You must use "MM" and not "mm" when converting a DateTime to a specific text format

oDataRow.Item("Birthday") = Me.dtpClientBirthday.Value.ToString("dd/MM/yyyy")

String to DateTime
String to TimeSpan