Check whether this date/time is earlier than another. The comparison takes time zones into account: if the two instances have different time zones, they are first converted to UTC before comparing. Note that if either instance is a local clock time (type ClockTime), the result cannot be guaranteed to be correct, since by definition they contain no information about time zones or daylight savings changes. If one or both instances are date-only, the comparison returns true if this date/time or day, falls wholly before the other date/time or day. To achieve this, the time used in the comparison is the end of day (if this instance is date-only) or the start of day (if the other instance is date-only). Create a separate copy of this instance's data if it is implicitly shared with another instance. You would normally only call this if you want different copies of the same date/time value to cache conversions to different time zones. Because only the last conversion to another time zone is cached, and the cached value is implicitly shared, judicious use of detach() could improve efficiency when handling several time zones. But take care: if used inappropriately, it will reduce efficiency!
