Amidora · Library
Count the civil dates and months in a Hebrew calendar year
Hebrew years 5784, 5785 and 5786 run 383, 355 and 354 days; list each month's civil dates and reconcile the counts with the gap between two 1 Tishrei dates.
How an inventory is built
An inventory takes the civil date of 1 Tishrei, steps forward one day at a time and converts each date until the next 1 Tishrei, which belongs to the following year. Each converted date is grouped by the month identifier it returns. The converter uses the calendar's own month names, so a leap year produces separate adar-i and adar-ii groups and a common year a single adar group.
Whether a year is a leap year follows the rule the tool itself applies: (7 × year + 1) mod 19 is below 7. For 5784 the remainder is 0, so the year has 13 months; for 5785 it is 7 and for 5786 it is 14, so both have 12.
Compare two complete civil-year inventories
| Hebrew year | First included civil date | Next year begins; excluded | Months | Days |
|---|---|---|---|---|
| 5784 | 2023-09-16 | 2024-10-03 | 13 | 383 |
| 5785 | 2024-10-03 | 2025-09-23 | 12 | 355 |
The fixed examples are Hebrew years 5784 and 5785. Their included civil dates are enumerated by the same converter used by the calendar tool. The next year’s first date belongs to the next inventory, so it is not counted twice.
Month counts in 5784
| Month ID | Month | First civil date | Last civil date | Days |
|---|---|---|---|---|
| tishrei | Tishrei | 2023-09-16 | 2023-10-15 | 30 |
| cheshvan | Cheshvan | 2023-10-16 | 2023-11-13 | 29 |
| kislev | Kislev | 2023-11-14 | 2023-12-12 | 29 |
| tevet | Tevet | 2023-12-13 | 2024-01-10 | 29 |
| shvat | Sh'vat | 2024-01-11 | 2024-02-09 | 30 |
| adar-i | Adar I | 2024-02-10 | 2024-03-10 | 30 |
| adar-ii | Adar II | 2024-03-11 | 2024-04-08 | 29 |
| nisan | Nisan | 2024-04-09 | 2024-05-08 | 30 |
| iyyar | Iyyar | 2024-05-09 | 2024-06-06 | 29 |
| sivan | Sivan | 2024-06-07 | 2024-07-06 | 30 |
| tamuz | Tamuz | 2024-07-07 | 2024-08-04 | 29 |
| av | Av | 2024-08-05 | 2024-09-03 | 30 |
| elul | Elul | 2024-09-04 | 2024-10-02 | 29 |
Month counts in 5785
| Month ID | Month | First civil date | Last civil date | Days |
|---|---|---|---|---|
| tishrei | Tishrei | 2024-10-03 | 2024-11-01 | 30 |
| cheshvan | Cheshvan | 2024-11-02 | 2024-12-01 | 30 |
| kislev | Kislev | 2024-12-02 | 2024-12-31 | 30 |
| tevet | Tevet | 2025-01-01 | 2025-01-29 | 29 |
| shvat | Sh'vat | 2025-01-30 | 2025-02-28 | 30 |
| adar | Adar | 2025-03-01 | 2025-03-29 | 29 |
| nisan | Nisan | 2025-03-30 | 2025-04-28 | 30 |
| iyyar | Iyyar | 2025-04-29 | 2025-05-27 | 29 |
| sivan | Sivan | 2025-05-28 | 2025-06-26 | 30 |
| tamuz | Tamuz | 2025-06-27 | 2025-07-25 | 29 |
| av | Av | 2025-07-26 | 2025-08-24 | 30 |
| elul | Elul | 2025-08-25 | 2025-09-22 | 29 |
Build one yourself
- Convert 1 Tishrei of the year and of the following year with the converter.
- Subtract the two civil dates to get the year length in days.
- List each month's first and last civil date, or count its days.
- Check that the month totals add up to the year length.
- Note whether the year shows one Adar or two.
Extending the table to 5786 and 5787
1 Tishrei 5786 is 2025-09-23 and 1 Tishrei 5787 is 2026-09-12. The difference is 354 days, one fewer than 5785. 5787 is a leap year by the remainder rule, (7 × 5787 + 1) mod 19 = 2, and the converter shows it: 2027-03-01 is 22 Adar I 5787, and 1 Adar II 5787 is 2027-03-10.
- 5786 · first day
- 2025-09-23
- 5787 · first day
- 2026-09-12
- Days in 5786
- 354
- 1 Adar II 5787
- 2027-03-10
Kislev shows the year-to-year difference in month length: Kislev 30 exists in 5785, on 2024-12-31, but not in 5784.
Mistakes
- Counting the next year's 1 Tishrei in the current year's total.
- Merging adar-i and adar-ii rows into one Adar.
- Assuming every Hebrew year has the same length or the same months.
- Mixing date-only results with times of day in the same table.
Boundary
The inventory is built from date-only UTC conversions. It does not mark when a religious day begins at sunset or which observance applies; the converter and the Hebcal documentation listed below cover only the civil-date arithmetic.