First you need to know these Lowe's or Home Depot type timers are always unpredictable and screwing up. I've not found a one that lasted more than one season. You seem to have gotten some great use out of yours! What I'd like to know is what it is you are watering, why you need it on a timer (are you away for your job)? Is this drip irrigation or overhead? How large of an area you water, are you on multiple timers? I am not a fan of automatic watering except for when one has to be absent. Hand watering is even worse.
Send pictures of what you are watering and tell us what your thinking is for schedule/timing/volume. How much water is delivered within a certain amount of time? Best way to test this without getting into water pressure/volume is to put out straight sided cans (kitty cat food cans are super) in many areas of your garden...water for 15 minutes and check the volume of water in your cans. If there is 1/4 inch of water then only 3 more waterings during the week will be suitable.
With drip irrigation this is tougher. Dig down into the soil to be able to see the depth of moisture after a period of time (15 minutes, half an hour). You want to work towards 1" per week or 4-6" deep each watering, allowing it to dry out before watering again. Depends on what you are watering; plants, lawns, vegey gardens, ornamental plant beds (mature plants and newbie plants); type of mulch, whether or not you (cross my fingers you haven't) have used plastic below the mulch. Send pictures!
What is your soil type? Have you had a soil test? What are you doing for fertilizer? Any other chemicals you've used? Sounds weird but watering habits affect all of these things.