Set early bird in registration using visual studio 2013 express for web

i just want to know what i should use in order to know someone is an 'early bird' when they did registration on a webpage.

Also,i'm using visual studio 2013 express for web and c# as coding language.

Once the system detect that person is an 'early bird', the system should print out type of registration as 'early bird'.

So right now i don't know what kind of procedure or algorithm or anyhing to use so that the system knows that person is an "early bird" when they did the registration. Any ideas?