Author: Jeff Guidotti

Here is a working example of how to use alternative date formats in the 
TDateTimePicker component for Delphi 5.

Answer:

The problem for me with the TDateTimePicker component, is that it would not only 
allow dates based on the Windows settings for ShortDate and LongDate, but it also 
left gaps in between the separators for dates like ' 2/ 3/01'. This made it look 
terrible.   

I did some research into the problem, and found many "solutions" that did not seem 
to work all the time.  So far, I haven't had any problems with this one, and 
although I tested it in Delphi 5, it should work in some previous versions. 

Simply enter the following line of code into the OnActivate Event for each 
TDateTimePicker on your form.  This will manually set the format, and it should 
remain in place until the form is destroyed. 
1   
2   DateTimePicker1.Perform(DTM_SETFORMAT, 0, DWORD(PCHAR('MM/dd/yyyy')));

The above example assumes that the TDateTimePicker is named DateTimePicker1, and 
you can vary the format by changing the format string ('MM/dd/yyyy'). 

I am not sure what format's are available, and it seems a bit quirky.  I had tried to use 'mm/dd/yyyy', and I wound up with a month of '52'!!!  The above string forces two digit months and days, and four-digit years.