Java Date cut off time information

The recommended way to do date/time manipulation is to use a Calendar object:

Calendar cal = Calendar.getInstance(); // locale-specific
cal.setTime(dateObject);
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
long time = cal.getTimeInMillis();

Have you looked at the DateUtils truncate method in Apache Commons Lang?

Date truncatedDate = DateUtils.truncate(new Date(), Calendar.DATE);

will remove the time element.

Have you looked at Joda ? It's a much easier and more intuitive way to work with dates and times. For instance you can convert trivially between (say) LocalDateTime and LocalDate objects.

e.g. (to illustrate the API)

LocalDate date = new LocalDateTime(milliseconds).toLocalDate()

Additionally it solves some thread-safety issues with date/time formatters and is to be strongly recommended for working with any date/time issues in Java.