Business is full of rhythms, too. If you identify the rhythms of your company's year, you can make sure your plans are in concert with those rhythms. Anything else is like trying to swim upstream. Your calendar is the long-range planning tool that lets you do this.
Every business has a light time of the year and a heavy time of the year. You can plan your system administration tasks and goals around these patterns.
I used to work at a software company that produced three software releases each year. Every 120 days, a new release would ship. The first month was mostly spent developing marketing requirements and feature lists. There were 60 days of development, two weeks of quality assurance (QA), and two weeks of manufacturing of the software and manuals. Day 120 was shipping day. Then the entire cycle began again. Because it ran like clockwork three times a year, it was a system administrator's dream.
During the first month of the cycle, most of the employees were in meetings and the network was quiet. As long as email was running, nearly any other function could be taken down for maintenance and upgrades. The "tool group" planned which OS/compiler releases would be used for the next version during the last days of the prior release cycle. The first month of the current cycle was when the system administration teams would deploy those tools. During the development stage, outages were tolerated if they were scheduled. Regular system administrator activity ...