Home Assistant makes negative offsets run before a sun or calendar event and positive offsets run after it. Anyone who wrote a sun.* or calendar.event_started or calendar.event_ended trigger with an offset but no offset_type needs to reverse the sign to preserve its timing.
Triggers created through the interface already stored an explicit before-or-after choice and keep working. The editor brings that choice into the offset field, while existing configurations with offset_type remain accepted.