The Date Nobody Set

The Date Nobody Set

On the third of February the bookkeeper sets her work date back to 31 January to finish the January close — exactly what the Work Date field on My Settings is for. Then everything goes wrong: every invoice she creates still defaults to 3 February, the "backdated document" warning fires on every January posting, and the overdue report counts three extra days on every open invoice.

The cause is one word. The code reads Today — the calendar clock — where it should read the session's work date: the date users set on My Settings, the one the w shortcut enters in any date field, and the one AL exposes through WorkDate. When nobody changes it, the work date is today, which is why the bug never showed up on the developer's machine.

Your job is a small codeunit that answers three everyday date questions from the work date.

Requirements

Create a codeunit named "Work Date Policy" with three public procedures:

procedure DefaultPostingDate(): Date
procedure IsBackdated(PostingDate: Date): Boolean
procedure DaysOverdue(DueDate: Date): Integer

Rules:

1. DefaultPostingDate returns the session's work date — never the calendar date.
2. IsBackdated returns true when PostingDate lies strictly before the work date. A posting date equal to the work date or after it is not backdated. A blank posting date (0D) is not backdated either — nothing has been entered yet, so there is nothing to flag.
3. DaysOverdue returns the number of whole days by which DueDate lies before the work date: a due date ten days before the work date is 10 days overdue. A due date on the work date, after the work date, or blank (0D) is 0 days overdue — the result is never negative.
4. The answers must follow the work date: when the work date moves, the same inputs give different answers. Reading the clock (Today, CurrentDateTime) cannot satisfy this — it agrees with the work date only on the one day nobody changed it.

Note the blank date: 0D is smaller than every real date, so a plain comparison would call it backdated and a plain subtraction would report it centuries overdue. Decide the blank case before you compare or subtract.

What the tests check

The grading tests set the work date themselves with WorkDate(20240115D) before each call and assert exact values against 15 January 2024: the default posting date is that date; 14 January 2024 and 31 December 2023 are backdated while 15 January, 16 January and a blank date are not; due dates of 5 January 2024 and 20 December 2023 are 10 and 26 days overdue, and the due date itself, a randomly chosen future due date and a blank due date are 0. Three further tests move the work date to a random day in 2019–2021 and expect the answers to move with it: the default posting date equals the new work date, a posting date after it is not backdated, and a due date a random number of days before it is overdue by exactly that many days. A solution based on Today fails those tests on every day of the year.

Pick object IDs in the range 50100–50199 and reference other objects by name, never by ID.

Learn More

• System.WorkDate([Date]) Method — reads and sets the session work date; the method the tests use to move it.
• System.Today() Method — what the clock actually returns, and why it depends on the user's time zone.
• About dates in Business Central — Microsoft's own note on the trouble with defaulting a posting date from Today.
• Change basic settings — Work date — where users set the work date and how the client shows that it differs from today.