---
bc-version: [all]
domain: architecture
keywords: [workdate, session-setting, user-control, side-effect]
technologies: [al]
countries: [w1]
application-area: [all]
---

# Application code must not change the WorkDate

## Description

The work date is a per-user session setting the user controls from the
client (the date shown in the top-right corner, used to default posting
dates and date filters). Microsoft's own Business Central standard is that
application code must never call the `WorkDate` function to set a new
value. Doing so changes what the user sees and defaults to for the rest of
their session, as a side effect of running unrelated business logic — a
surprising, hard-to-trace behavior change the user never asked for and has
no visibility into.

This is a call-direction distinction: reading the current work date via
`WorkDate` (or `WorkDate()` with no argument) is fine and common — it is
only the assignment form, `WorkDate(NewDate)`, that is the anti-pattern.

## Best Practice

```al
PostingDate := WorkDate();
```

Read the work date to default a value; never write to it.

## Anti Pattern

```al
WorkDate(CalcDate('<1D>', WorkDate()));
```

Setting the work date from within a codeunit, report, or page action
changes session state the user owns, for the duration of a call that has
nothing to do with the user's date preference. If a scenario genuinely
needs a specific date for a calculation, pass or compute that date as a
local variable — never repurpose the session's `WorkDate`.