# define a format that is supported by our attribute
$stringDate = '4/14 4:12PM'
# try it first with the normal datetime type
[datetime]'4/14 4:12PM'
# this threw an error

# define a variable that utilizes the attribute
[datetime][DateTransform()]$dt = $stringDate
# no error 
$dt

# now let's add another format string utilizing the parameter of our custom attribute
# note that the parameter accepts an array arguments. The argument(s) need to be always put in parenthesis for an array argument.
[DateTransformAttribute(('xxx dd.MM hh:mm'))]$dt2 = 'xxx 15.12 10:45'
$dt2