Question: I can calculate the time in milliseconds with the following Ruby snippet:

```ruby
$ irb
> require 'date'
 => true 
> Date.new(2014,9,5).to_time
 => 2014-09-05 00:00:00 +0200
> Date.new(2014,9,5).to_time.to_i * 1000
 => 1409868000000

```

`1409868000000` is the desired result.  

How can I get the same result with Java? I set the time zone to [CEST](http://www.timeanddate.com/library/abbreviations/timezones/eu/cest.html) since it seems to be what Ruby works with. So I tried this:

```java
GregorianCalendar calendar = new GregorianCalendar(TimeZone.getTimeZone("CEST"));
calendar.set(2014, 9, 5);
System.out.println("" + calendar.getTimeInMillis());
// Returns: 1412498241422

```

Answer: 
There are three problems with your current code:

* "CEST" isn't a time zone Java recognized. Try `Europe/Paris` instead, as a European time zone
* `java.util.Calendar` uses 0-based months (yes, it's awful)
* You haven't cleared out the time part of the `Calendar`, so it'll give you the current time of day, on that date

This works:

```
import java.util.*;

public class Test {
    public static void main(String[] args) throws Exception {
        TimeZone zone = TimeZone.getTimeZone("Europe/Paris");
        Calendar calendar = new GregorianCalendar(zone);
        // Month 8 = September in 0-based month numbering
        calendar.set(2014, 8, 5, 0, 0, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        System.out.println(calendar.getTimeInMillis());
    }
}

```

If you *know* the month in advance, you can use the constants instead:

```
calendar.set(2014, Calendar.SEPTEMBER, 5, 0, 0, 0);

```

If you can possibly move to using [Joda Time](http://joda.org/joda-time) or `java.time` from Java 8, however, those are much cleaner APIs.

For example, in Joda Time:

```
import org.joda.time.*;

class Test {
    public static void main(String[] args) {
        DateTimeZone zone = DateTimeZone.forID("Europe/Paris");
        // Look ma, a sensible month numbering system!
        LocalDate date = new LocalDate(2014, 9, 5);
        DateTime zoned = date.toDateTimeAtStartOfDay(zone);
        System.out.println(zoned.getMillis());
    }
}

```
try

```
calendar.set(2014, 8, 5, 0, 0, 0);
System.out.println("" + (calendar.getTimeInMillis() / 1000) * 1000);

```

see <http://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html#set(int,%20int,%20int,%20int,%20int)>