This is a wheel that\'s been re-invented again and again over the years.
The Problem: The user needs to input a Date/Time
Basic considerations
You need to check your UI requirements. If you want script-enabled support only, they you can go with any of your panopoly of scripts and run with whatever date/time format they provide into a hidden field.
However, if you need the user entry in a textbox, then you're faced with some decisions:
Validation methods depend on your decisions on requirements.
I like the jQuery date-picker plugin. It'll allow output in specific formats.