import static java.lang.annotation.RetentionPolicy.RUNTIME;
DateTimeto an offset relative to the current system time. Basicly the
DateTimein millis will be System.currentTimeMillis() + offset. The offset is calculated as a
Periodin years, months, days, hours, minutes, seconds, weeks and millis. Which means the user doesn't have to calculate the offset for a given year, but can just set the years value to -1 to go back one year in time.