As Manish's sample show you won't need Floor() function here. Floor is needed when converting from TimeStamp Field to Date Field. For extracting just Year (or month or day) you would just need to wrap is around with Year() (or Month() or Day()) functions.
the only thing to make sure is that QV reads your date as true date (and not as a string). If for some reason it isn't read as a date you can use Date#() function to help it understand that it is actually a date. (Why don’t my dates work?)
Make use of the year(date) function to create a year field. There are umpteen number of date functions which would be of great help in Qlik check this document for more information: