Android : Check if timestamp (milli) belongs to a specific day

In a table of my SQLite database there is a timestamp (millisec) column. This table is really huge and I want a efficent way of querying all the rows that theire timestamp column refers to a specific day (in this case I want to get all enteries that belong to TODAY).

I came up with this, but it does not work and its quite slow. Any ideas will be appriciated. (NO I can not make any change in the database such as adding a DATETIME column...I have to do it with the timestamp).

public boolean isTimestampInToday(long timestamp){

    //get a timestamp from today
    long todayStamp = System.currentTimeMillis();

    Calendar c = Calendar.getInstance();
    c.setTimeInMillis(todayStamp);
    c.setTimeZone(TimeZone.getDefault());

    c.set(Calendar.HOUR_OF_DAY, 0);
    c.set(Calendar.MINUTE, 0);
    c.set(Calendar.SECOND, 0);
    c.set(Calendar.MILLISECOND, 0);

    Date startDate = c.getTime(); //START OF DAY

    c.set(Calendar.HOUR_OF_DAY, 23);
    c.set(Calendar.MINUTE, 59);
    c.set(Calendar.SECOND, 59);
    c.set(Calendar.MILLISECOND, 999);

    Date endDate = c.getTime(); //END OF DAY

    Long startStamp = startDate.getTime();
    Long endStamp = endDate.getTime();

    if(timestamp >= startStamp && timestamp < endStamp) {
        return true;            
    } else {
        return false;
    }      
}