Java – what happened to “2017-9-21 23:59”?

I used a calender for one minute at a time But something strange happened on the date of "2017-9-21 23:59" The date came back an hour It acts like a date to save time, but save time dates must not occur

This is my code and output:

GregorianCalendar fromCalendar = new GregorianCalendar(2017,8,21,22,58);

    for (int i = 0; i < 120; i++) {
        System.out.println(fromCalendar.get(Calendar.YEAR) + "-"
                + (fromCalendar.get(Calendar.MONTH) + 1) + "-" +   fromCalendar.get(Calendar.DAY_OF_MONTH) + " "
                + fromCalendar.get(Calendar.HOUR_OF_DAY) + ":" + fromCalendar.get(Calendar.MINUTE) + "      ");
        fromCalendar.add(Calendar.MINUTE,1);
    }

Output:

.
.
.
2017-9-21 23:58     
2017-9-21 23:59     
2017-9-21 23:0      
2017-9-21 23:1      
2017-9-21 23:2  
.
.
.

Is there any simple point I misunderstood?

Solution

According to the timeanddate Com DST page, there is only one country in the world whose DST conversion takes place in Iran at 00:00 on September 22, 2017

Therefore, you must use the timezone for Iran: Asia / Tehran