来自开发者博客:

System.currentTimeMillis() is the standard "wall" clock (time and date) expressing milliseconds since the epoch. The wall clock can be set by the user or the phone network (see setCurrentTimeMillis(long)), so the time may jump backwards or forwards unpredictably. This clock should only be used when correspondence with real-world dates and times is important, such as in a calendar or alarm clock application. Interval or elapsed time measurements should use a different clock. If you are using System.currentTimeMillis(), consider listening to the ACTION_TIME_TICK, ACTION_TIME_CHANGED and ACTION_TIMEZONE_CHANGED Intent broadcasts to find out when the time changes.

1320917972是从1970年1月1日00:00:00 UTC开始使用秒数的Unix时间戳。您可以使用TimeUnit类进行单位转换——从System.currentTimeMillis()转换为秒。

String timeStamp = String.valueOf(TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis()));

它的用法很简单:

long millis = new Date().getTime();

如果你想在特定的格式，那么你需要像下面这样的Formatter

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String millisInString  = dateFormat.format(new Date());

来自开发者博客:

System.currentTimeMillis() is the standard "wall" clock (time and date) expressing milliseconds since the epoch. The wall clock can be set by the user or the phone network (see setCurrentTimeMillis(long)), so the time may jump backwards or forwards unpredictably. This clock should only be used when correspondence with real-world dates and times is important, such as in a calendar or alarm clock application. Interval or elapsed time measurements should use a different clock. If you are using System.currentTimeMillis(), consider listening to the ACTION_TIME_TICK, ACTION_TIME_CHANGED and ACTION_TIMEZONE_CHANGED Intent broadcasts to find out when the time changes.

你可以使用SimpleDateFormat类:

SimpleDateFormat s = new SimpleDateFormat("ddMMyyyyhhmmss");
String format = s.format(new Date());

我建议使用Hits的答案，但添加一个Locale格式，这是如何Android 开发人员建议:

try {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
        return dateFormat.format(new Date()); // Find todays date
    } catch (Exception e) {
        e.printStackTrace();

        return null;
    }