public long getExpirationTime() throws EntryNotFoundException {
    long ttl = getTTLExpirationTime();
    long idle = getIdleExpirationTime();
    if (ttl == 0) {
      return idle;
    } else if (idle == 0) {
      return ttl;
    }
    return Math.min(ttl, idle);
  }
@return the absolute time (ms since Jan 1, 1970) at which this region expires, due to either
        time-to-live or idle-timeout (whichever will occur first), or 0 if neither are used.
geode-core/src/main/java/org/apache/geode/internal/cache/ExpiryTask.java