What potential pitfalls or drawbacks may arise from using a timestamp check instead of cronjobs for database updates?

One potential pitfall of using a timestamp check instead of cronjobs for database updates is that it may not be as reliable or precise in scheduling the updates. If the timestamp check is dependent on user activity or server load, the updates may not occur at the exact time intended. To solve this issue, you can combine the timestamp check with a cronjob that triggers the update script at regular intervals.

```php
// Check if it's time to run the database update
if (time() >= strtotime('2022-01-01 00:00:00')) {
    // Run the database update script
    include 'database_update_script.php';
}
```
In this code snippet, we use a timestamp check to determine if it's time to run the database update. However, to ensure the update is executed reliably and at regular intervals, you can set up a cronjob to trigger the script periodically.