Most airlines tweak their schedules seasonally, adding some flights, changing the times of some flights, cancelling some flights. This is normal. I never expect to really know my flight numbers and times more than 3 months out. Anything booked before then I expect to change, although hopefully by not more than an hour or so. The problem seems to be, though, that airlines are now changing their schedules closer and closer to departure date, and with larger swings in times, so you can't really be confident in your flight times until the day of!
But - as I said in my previous post - if you don't like your new flight times, take it up with the airline and stand your ground, even when they give you something like the we-have-the-right-to-change-things-by-up-to-x-hours line. Don't get nasty, but just insist that there is no way you would EVER have booked flights at the times they now have you at. Give them a concrete reason why it is a problem other than it's inconvenient to you - e.g. you are travelling with young children and can't take an extremely early/late flight, you have issues with transportation to/from the airport at the new hours, you have an appointment that cannot be moved, etc. If the agent you are speaking to keeps giving the same can't-do-anything-for-you line, try "So there is NOTHING you can do for me?" - for some reason, that line seems to work alot for me. Maybe it's because you are calling them directly on their refusal to be of service. Who knows. But if that still doesn't work, ask to speak to a supervisor or ask for the customer complaints department number - again, nicely but firmly.
I've never had a problem getting flights I find more acceptable taking the above approach. Sometimes it takes a few calls, but eventually I find someone willing to work with me.