Save perhaps in the case of changes to the first sector, date/time changes do not require a ticket re-issue. The e-ticket just needs to be revalidated.

Route changes require ticket re-issue.

checkmytrip will be no help in telling you whether the e-ticket has been revalidated properly, but usually that doesn't matter because a date/time change won't cause too many problems at the airport to get sorted. Re-routes do.