THE old Persian year was solar and began at the vernal equinox. It consisted of 365 days divided into 12 months of 30 days each, the five extra days being added after the completion of the twelfth month to fill up the time till the sun should re-enter Aries, and spring and the new year begin on the 21st of March. Each day of the month had its special genius presiding over it, after whom it was named, thus:—
| Day 1. | Urmuzd. | Day 16. | Mihr. |
| Day 2. | Bahman. | Day 17. | Surúsh. |
| Day 3. | Ardibihisht. | Day 18. | Rashn. |
| Day 4. | Sharívar. | Day 19. | Farvardín. |
| Day 5. | Sapandármad. | Day 20. | Bahrám. |
| Day 6. | Khurdád. | Day 21. | Rám. |
| Day 7. | Murdád. | Day 22. | Bád. |
| Day 8. | Dai pa Ádar. | Day 23. | Dai pa Dín. |
| Day 9. | Ádar. | Day 24. | Dín. |
| Day 10. | Ábán. | Day 25. | Ard. |
| Day 11. | Khurshíd. | Day 26. | Áshtád. |
| Day 12. | Máh. | Day 27. | Ásmán. |
| Day 13. | Tír. | Day 28. | Zamíyád. |
| Day 14. | Gúsh. | Day 29. | Máhraspand. |
| Day 15. | Dai pa Mihr. | Day 30. | Anairán. |
Of these thirty genii twelve were chosen to give their names to the months as well, thus:—
| PRING . | { | Farvardín . . . | March 21 | to April 19. |
| Ardibihisht . . . | April 20 | to May 19. | ||
| Khurdád . . . . | May 20 | to June 18. | ||
| SUMMER . | { | Tír . . . . . . | June 19 | to July 18. |
| Murdád . . . . | July 19 | to August 17. | ||
| Sharívar . . . . | August 18 | to September 16. | ||
| AUTUMN . | { | Mihr . . . . . | September 17 | to October 16. |
| Ábán . . . . . | October 17 | to November 15. | ||
| Ádar . . . . . | November 16 | to December 15. | ||
| WINTER . | { | Dín . . . . . | December 16 | to January 14. |
| Bahman . . . . | January 15 | to February 13. | ||
| Sapandármad . . | February 14 | to March 15. |
Thus the day Sapandármad of the month Khurdád would be equivalent to May 24th, and the day Khurdád of the month Sapandármad to February 19th.
Time was reckoned by days and nights, not by nights and days as among the Jews and Muhammadans.
The twenty-four hours of the day and night were divided into eight watches of three hours each.