I am paid a salary, and it's understood by my employer and I that some business days I may work less than 8 hours and some business days I may work more, some d

I am paid a salary, and it's understood by my employer and I that some business days I may work less than 8 hours and some business days I may work more, some days I may arrive later and leave later, and some earlier, and additionally I may work on weekends and holidays. So, my employer doesn't really have a leg to stand on if they say that I used time I sold to them to pursue my own interests, because there is no explicit agreement that any specific amount (or "non-fungible unit") of my time is theirs. Neither can they say I used their equipment or resources, if I didn't. What basis remains upon which they can claim that I used "their" time and/or their resources and/or their equipment to conduct personal business?