Why does sdf.format(date) converts 2018-12-30 to 2019-12-30 in java? [duplicate]

Answer 1

You don't need to format the date again with SimpleDateFormat. Just use as follows.

Date format required : 2019-12-30

The appropriate date format specified will be : yyyy.MM.dd (yyyy : Represents full year)

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = simpleDateFormat.parse("2018-12-30");
String sDate = simpleDateFormat.format(date);

Answer 2

Case-sensitive

Uppercase YYYY means year of a week-based year rather than a calendar year (lowercase yyyy).

So you are seeing a feature, not a bug. The second to the last day of 2018 is in the first week of 2019 according to the definition of a week used by SimpleDateFormat. That definition varies by Locale.

Avoid legacy date-time classes

You are using terrible date-time classes that were supplanted years ago by the modern java.time classes defined in JSR 310.

LocalDate

The LocalDate class is appropriate to your string inputs.

String input = "2019-12-30" ;
LocalDate ld = LocalDate.parse( input ) ;

Answer 3

Where sdf is setup?? Just use fmt it will works fine. Try Following.

SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
Date date = fmt.parse("2018-12-30");
String date2 = fmt .format(date);