When I got my promotion, we hired a replacement to fill my old position. In training him, we purposely taught him how to do 75% of my job and 100% of his job so that he could back me up when I need a break and I could support him in return. And, since we share an office, it's easy for us to seamlessly blend some of our duties. Yet there are some things (due to time, scheduling, and access constraints) that he's not able to handle when I am gone.
The biggest gap that he can't cover are my morning reports. Business needs dictate one of the two of us are staffed during late afternoon into the evening; when I take vacation, there's no one staffed in our cubicle during the morning hours. There is a report that he and I update throughout the day and the first thing I do every morning is send out the completed report for the previous day. Then I restart the same report with the current day's data. This is all done before my cohort arrives. In my morning reports, the previous day's data is due early in the a.m. but the other half can wait until later in the day. So those two parts are to be split between my office mate and someone else.
Before I left for work this afternoon, I tried my best to explain the division of labor. When I let him know who was covering the "previous day" portion and that the "current day" was the only extra effort he'd have to make, we had the following conversation:
Me: She's going to do yesterday's report tomorrow so that you don't have to.
Him: Didn't you do yesterday's report this morning?
Me: I did yesterdays, but tomorrow that was two days ago. Today is tomorrow's yesterday.
Him: So who will do today's report?
Me: She will. All you'll have to do beyond what you normally do is create today's report.
Him: Isn't she doing that?
Me: No, she's doing yesterday's with today's numbers. You'll do the new report tomorrow.
Him: With today's data?
Me: Right. Only with tomorrows data. Because tomorrow will be today.
And he understood what I was talking about.