The conversion of date value, in:
dim datevariable as date = Now
sformat = sFormat
msgbox (datevariable.ToString(sFormat))
or in
Text="{Binding Path=[linkObject.modifiedDate], Converter={StaticResource StringFormatValueConverter}, ConverterParameter=\{0:sFormat\}}" />
The results are:
sFormat  | 
Result  | 
d  | 
11/05/2007  | 
D  | 
May 11, 2007  | 
t  | 
9:09 PM  | 
T  | 
9:09:27 PM  | 
f  | 
May 11, 2007 9:09 PM  | 
F  | 
May 11, 2007 9:09:27 PM  | 
g  | 
11/05/2007 9:09 PM  | 
G  | 
11/05/2007 9:09:27 PM  | 
M  | 
May 11  | 
R  | 
Fri, 11 May 2007 21:09:27 GMT  | 
s  | 
2007-05-11T21:09:27  | 
u  | 
2007-05-11 21:09.27z  | 
U  | 
May 12, 2007 4:09:27 AM  | 
y  | 
May, 2007  | 
dd  | 
11  | 
ddd  | 
Fri  | 
dddd  | 
Friday  | 
HH:mm:ss.fff z  | 
21:09:69.275 -7  | 
yy/MM/dd g  | 
07/05/11 A.D.  | 
Other examples
See http://www.java2s.com/Tutorial/VB/0100__Date-Time/Useformatspecifierstocontrolthedatedisplay.htm