Mac OS 9: How to Set Date and Time to ISO 8601:1988 Standard
1. Open the Date & Time control panel.
2. Click Date Formats. The Date Formats window appears.
3. In the Long Date area, set the pop-up menus to this order:
4. Delete the comma in the field next to the Month pop-up menu.
5. Click the checkbox to enable "Leading zero for day".
6. In the Short Date area, choose Year/Month/Day from the pop-up menu.
7. Type a hypen in the Separator field.
8. Click the checkboxes to enable "Leading zero for day", "Leading zero for month", and "Show century".
When you have finished these steps, your settings should look like those in Figure 1.
Figure 1 Date Formats window
9. Click OK.
10. Click Time Formats. The Time Formats window appears.
11. Click 24 hour.
12. Click the checkbox to enable "Use leading zero for hour".
When you have finished these steps, your settings should look like those in Figure 2.
Figure 2 Time Formats window
13. Click OK.
14. Close the Date & Time control panel.
For more information on the ISO 8601:1988 standard, Open Sherlock 2 and search for ISO 8601.