Why Microsoft Access File Timestamps Change When Opened
Question details
The user wants to understand why Microsoft Access updates the last modified timestamp of an ACCDB or MDB file merely by opening it, even if no database content is altered.
- Product
- Microsoft Access
- Device & OS
- not provided
- Scenario
- Opening an existing ACCDB or MDB database file to view contents.
- Observed behavior
- The operating system's file modified timestamp changes immediately upon opening the database, making it difficult to rely on OS file properties for version tracking.
Before investigating timestamp changes, ensure that no background macros or startup scripts are intentionally modifying data upon opening the database.
Understand Access Behavior and Use File Name Timestamps
Microsoft Access inherently updates system tables upon opening, which alters the file modified date. Using a naming convention is the best workaround.
By default, Access updates the DateUpdate value for the MSysDb system table within MSysObjects every time a database is opened. This causes the operating system to update the file's 'Date Modified' property, even if you make no changes.
Experienced developers recommend not relying on the OS modified date for ACCDB or MDB files due to this hard-coded behavior.
Rename your Access database files to include the date and time manually or via a script (e.g., DatabaseName_20231024_1030.accdb).
Keep older versions in a separate archive folder to maintain a clear history instead of relying on file properties.
Check Actual Object Modification Dates using SQL
If you need to know when actual tables or queries were last changed, you can query the internal system table to view individual object updates.
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Frequently Asked Questions
Can I stop Access from updating the modified date when opening?
No, this is a built-in behavior of Microsoft Access. The engine inherently updates internal system tables (like MSysDb) upon opening the file, which triggers a change in the operating system's file modified timestamp.
Do object-level dates change when the file timestamp changes?
No, individual database objects such as tables, queries, and forms maintain their own specific update dates. These remain unchanged unless you explicitly modify the object's design or properties.
How can I accurately track versions of my ACCDB files?
Because you cannot rely on the Windows 'Date Modified' property, the best practice is to append a timestamp (e.g., YYYYMMDD_HHMM) directly to the file name whenever you create a new version of the database.
