iOS Date() returns incorrect value

I am using the below code to get the iOS device date.

    let today = Date()
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "dd"
    let currentDate = dateFormatter.string(from: today)
    print("todayDate : \(currentDate)")
    dateFormatter.dateFormat = "MM"
    let currentMonth = dateFormatter.string(from: today)
    print("currentMonth : \(currentMonth)")
    dateFormatter.dateFormat = "YYYY"
    let currentYear = dateFormatter.string(from: today)
    print("currentYear : \(currentYear)")

When I am changing device date in iPhone setting 29-12-2019 or 30-12-2019 or 31-12-2019. currentMonth and currentDate values are correct. but, the currentYear return value is 2020 instead of 2019. Kindly suggest me to solve this issue.

Solution

A common mistake is to use YYYY. yyyy specifies the calendar year whereas YYYY specifies the year (of “Week of Year”), used in the ISO year-week calendar. In most cases, yyyy and YYYY yield the same number, however they may be different. Typically you should use the calendar year. see this for help : Challenges of DateFormatters

use your dateformat

"yyyy" is ordinary calendar year.

dateFormatter.dateFormat = "yyyy"

instead of

"YYYY" is week-based calendar year.

dateFormatter.dateFormat = "YYYY"

finally as per your question ,

   let today = Date()
   let dateFormatter = DateFormatter()     
   dateFormatter.dateFormat = "yyyy"
   let currentYear = dateFormatter.string(from: today)
   print("currentYear : \(currentYear)")

you get the output as