This rule is for managers and others who do not have full control of their time. I developed this ‘rule’ 15 years ago when I was managing an IT department with 20 associates, 200 projects, and 2000 computers…and I learned this lesson the hard way. Often, due to the number of meetings I had to attend, 80% to 90% of my day was scheduled by other people from other areas of the firm. So, when a crisis occurred, and these did happen more frequently than one would care to admit, either my staff would not alert me until I was available or I had to excuse myself from another appointment to attend to the urgent issue.
The 70/30 Rule of Time turned out to be the cure. I decided that only 70% of my time was available to others for meetings, etc. I reserved 30% of my daily calendar, including my lunch hour, for myself to allow for flexibility. I pre-scheduled my calendar so I had time in the morning and afternoon to react to the unforeseeable problems that can suddenly arise.
Of course, when there was no emergency, this reserved time was not idle. I would use it to be pro-active on important projects or to go over questions with others on my team.
If you have a hectic schedule that has many unknowns or you do not have full control of your time, try employing the 70/30 Rule of Time.