Just the other day I happened to notice my 6AM DFW-SFO flight was cancelled and they put me on a later flight, giving me an hour (instead of 3) to connect to the morning SIN flight.
No email notification, no "schedule change" notice in red....Nothing.
When I called to change my flights the agent said it was changed over a month ago.
(Luckily she cleared UG space for me on both flights without any arguing or begging on my part)