Current Time In Java(Logic Error) Time Zone: US Eastern Time

Question

I seem to have a logic error in my code. The time now is: 14:38, but my code says 18:38. I know there's a Calendar class I could use, but I want to know why this code was wrong.

Code below:

public class welcome{
  public static void main(String args[]){
    //get total milliseconds since 1970
    long total_millisec = System.currentTimeMillis();

    // compute total seconds since 1970
    long total_sec = total_millisec / 1000;

    //compute current second
    long current_sec = total_sec % 60;

    //compute total minutes since epoch
    long total_mins =  total_sec / 60;

    //compute current minute
    long current_min = total_mins % 60;

    //compute total hours
    long total_hours = total_mins / 60;

    //compute current hour
    long current_hour = total_hours % 24;

    System.out.println("Time is: "+current_hour+":"+current_min+":"
    +current_sec);

    }

 }

Which timezone are you in? ``System.currentTimeMillis()`` returns the milliseconds since 1.1.1970 *UTC*. — f1sh, Apr 01 '16 at 18:44
Nice! So there's more computation to be done to get it to ET — BattleDrum, Apr 01 '16 at 18:46
As f1sh already commented, `System.currentTimeMillis()` gives you a value offset to `UTC` (and EST is UTC-5, EDT is UTC-4). — Elliott Frisch, Apr 01 '16 at 18:46
Note the use of Java's locale in the date formatter here: http://stackoverflow.com/questions/4594519/how-do-i-get-localized-date-pattern-string Your locale is what you'd use to tell other Java code that you're in EST. — LinuxDisciple, Apr 01 '16 at 18:49

score 1 · Answer 1 · answered Apr 01 '16 at 19:24

When you perform your calculation, it's presumed that System.currentTimeMillis() returns difference in milliseconds between midnight of 1st January of 1970 (which is 1970-01-01 00:00) and current time. Try to evaluate the base date in your system and see what it'll be:

System.out.println("" + new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm").format(new java.util.Date(0)));

it might return something like 1969-12-31 19:00 and this is not the midnight.

System.currentTimeMillis() returns the same as expression:

long currentTime = new java.util.Date().getTime() - new java.util.Date(0).getTime();

Current Time In Java(Logic Error) Time Zone: US Eastern Time

1 Answers1