Tax Night

The last piece of paperwork I needed to do our 2014 income taxes arrived in today's mail, so I spent the evening dealing with TurboTax. To my annoyance, while I'm due a Federal refund, I owe non-resident income tax to California. Also, I find that for allocation-of-income purposes, I have to count every day I'm in California regardless of whether I earned income on that day if I have any California earned income. This doesn't seem particularly fair to me. I can understand taxing me on the days I'm working there, but why should I owe income tax to a state in which I don't live for days that I'm present in the state and not earning anything there, either?

I'm thinking I need to contact my employer and adjust down the percentage that they have me in California (it was 50% last year and will be 33% this year) but also have them over-withhold California income tax, lest I end up owing money again next year.