Do it on a date, or by a date

Every list gives you one field, “due date”, and asks it to carry two different promises. An appointment happens on a date. A deadline happens by a date. Put both in the same field and every item on the page looks equally urgent, which means none of them is.

One field, two promises

Take two entries from an ordinary week. The dentist is Tuesday at 3. The tax return is due Friday. Both sit in the same column and both carry a date, but they are not the same animal.

On: fixed

Doing something on a date means it happens Tuesday at 3, or it doesn’t happen. Appointments, calls, events, a train. The date is the thing itself, and the time is part of the date. Miss it and it’s gone. You can rebook the dentist, but you can’t be on time for the original.

An “on” item asks one thing of you: be there. Nothing before the date can substitute for it, and nothing after the date can rescue it.

By: flexible

Doing something by a date means any time before Friday counts. Deadlines, returns, renewals, the form that needs posting. The date is the edge of a window, not a point in it. You can do it Monday, Wednesday or Thursday evening, and all three are the same as far as the deadline is concerned.

Miss it, and it is late, not gone. The return can still be filed, the parcel can still go back, and the renewal can still be paid, perhaps with a small fee and a worse mood. A “by” item slips; an “on” item ends. (For why “by” items slip so reliably, see the planning fallacy. For what to do when one does, see late is not a failure state.)

What collapsing them costs

Merge the two and the list loses the information that tells you what to do first. Say a flight and a form both show “Friday”. One of them needs you in a particular seat at a particular time, and the other can be done in any spare 20 minutes before then. The list can’t say which is which, so you have to remember, and remembering is the job the list was meant to take over.

The usual result is a page where everything looks equally pressing. You respond to that the way anyone responds to a row of identical alarms: you stop hearing them. The calendar starts to read like fiction, because some of its dates are promises and some are guesses, and it has never said which.

The two teams

The strongest objection comes from a real argument among people who keep lists, and it has two sides.

Team A dates everything. A task without a date, they say, is a wish. Give “read that article” a day and it has a chance of happening. Leave it floating and it will float for ever.

Team B dates only true deadlines. A calendar full of fake deadlines, they say, teaches you to ignore the real ones. If every Thursday carries nine things that were never really due, the day the tax return is due looks like every other Thursday.

Both teams are describing something that happens. And the on/by split answers both of them at once.

Team A is right that a floating task tends to stay floating. But look at what the date on “read that article” is. Nobody is waiting for you on Wednesday. It is a “by” date you picked yourself, a window you drew around a task so it would stop floating. It is allowed to slip. Where Team A goes wrong is in letting that invented date sit in the same field as the dentist, so it borrows the dentist’s authority.

Team B is right that fake deadlines corrode the real ones. But the corrosion comes from the shared field, not from the dating. A self-chosen “by” date and an “on” date only look alike when they are written in one column. Write them in two and the invented date can no longer pass for a promise made to someone else.

So Team A keeps its dates, as “by” dates, and Team B keeps its meaning, because “on” stays reserved for the things that really happen on a day. Neither needs to give anything up. They only need somewhere separate to put it. When you sit down for your weekly review, sorting each item into one column or the other is most of the work.

Two columns

You don’t need new software for this. Open a notebook and rule a line down the middle of the page. Head the left column on and the right column by.

Under on, write the things that happen at a time: Tuesday at 3, the call at 11, the flight. Under by, write the things that must be done before a day, with the day beside them. Anything that has no date at all stays off both columns for now, until you decide which kind it is.

Then look at the week. The left column tells you where you have to be. The right column tells you what has room to move, and the dates in it tell you how much. The page no longer treats a Friday filing and a Friday flight as one kind of thing.

Take your list from this week and sort it into two columns on one page. Which column has been getting ignored?