| Code Figure | Meaning |
|---|---|
| 0 |
Gregorian |
| 1 | 360-day |
| 2 |
365-day (see Note 1) |
| 3 |
Proleptic Gregorian (see Note 2) |
| 4-191 | Reserved |
| 192-254 | Reserved for Local Use |
| 255 | Missing |
| Notes: (1) Essentially a non-leap year (2) Extends the Gregorian calendar indefinitely in the past |