By default, week numbers are not shown in the Date Navigator in the Calendar. You can change this behavior to show week numbers in the Date Navigator by enabling this setting.
| Registry Hive | HKEY_CURRENT_USER |
| Registry Path | Software\Policies\Microsoft\Office\12.0\Outlook\Options\Calendar |
| Value Name | WeekNum |
| Value Type | REG_DWORD |
| Enabled Value | 1 |
| Disabled Value | 0 |