Events that are so distant from each other that signals from one cannot reach the other within the time interval occupied by these events are not copresent. Thus, to take an example, a concert in Boston can be copresent with a soccer match in Sydney, but not with a soccer match on, say, Alpha Orionis: the present as it is defined relative to the soccer match extends some ninety light minutes into space, and so includes Sydney, but not Alpha Orionis, which is several hundred light years away.
Source: wiktionary