Английская Википедия:360-day calendar
Шаблон:Short description The 360-day calendar is a method of measuring durations used in financial markets, in computer models, in ancient literature, and in prophetic literary genres.
It is based on merging the three major calendar systems into one complex clockШаблон:Citation needed, with the 360-day year derived from the average year of the lunar and the solar: (365.2425 (solar) + 354.3829 (lunar))/2 = 719.6254/2 = 359.8127 days, rounding to 360.
A 360-day year consists of 12 months of 30 days each, so to derive such a calendar from the standard Gregorian calendar, certain days are skipped.
For example, the 27th of June (Gregorian calendar) would be the 4th of July in the USA.
Ancient Calendars
Ancient calendars around the world initially used a 360-day calendar.[1]
Rome
According to Plutarch's Parallel Lives Romans initially used a calendar which had 360 days, with varying length of months.[2] However, Macrobius' Saturnalia and Censorinus' The Birthday Book, claim that the original Roman calendar had 304 days split into 10 months. [3]
India
The Rig Veda describes a calendar with twelve months and 360 days.[4]
Mesoamerica
In the Mayan Long Count Calendar, the equivalent of the year, the tun, was 360 days.[5]
Egypt
Ancient Egyptians also used a 360-day calendar. One myth tells of how the extra 5 days were added.
Financial use
A duration is calculated as an integral number of days between startdate and enddate B. The difference in years, months and days are usually calculated separately:
- <math>duration(A,B) = (B_y - A_y) \times 360 + (B_m - A_m) \times 30 + (B_d - A_d); A \le B</math>
There are several methods commonly available which differ in the way that they handle the cases where the months are not 30 days long, i.e. how they adjust dates:
- European method (30E/360)[8][9][10][11][12]
- If either date A or B falls on the 31st of the month, that date will be changed to the 30th.
- Where date B falls on the last day of February, the actual date B will be used.
- All months are considered to last 30 days and hence a full year has 360 days, but another source says that February has its actual number of days.
- US/NASD method (30US/360)[13]
- If both date A and B fall on the last day of February, then date B will be changed to the 30th.
- If date A falls on the 31st of a month or last day of February, then date A will be changed to the 30th.
- If date A falls on the 30th of a month after applying (2) above and date B falls on the 31st of a month, then date B will be changed to the 30th.
- All months are considered to last 30 days and hence a full year has 360 days.
- ISDA method[14][10][11][12]
- If date A falls on the 31st of a month, then date A will be changed to the 30th.
- If date A falls on the 30th of the month after applying the rule above, and date B falls on the 31st of the month, then date B will be changed to the 30th.
- All months are considered to last 30 days except February which has its actual length. Any full year, however, always counts for 360 days.
- BMA/PSA method[10][11][12]
- If date A falls on the 31st of a month or last day of February, then date A will be changed to the 30th.
- If date A falls on the 30th of the month after applying the rule above, and date B falls on the 31st of the month, then date B will be changed to the 30th.
- All months are considered to last 30 days and hence a full year has 360 days.
- Alternative European method (30E+/360)[10][12]
- If date A falls on the 31st of a month, then date A will be changed to the 30th.
- If date B falls on the 31st of a month, then date B will be changed to the 1st of the following month.
- Where date B falls on the last day of February, the actual date B will be used.
- All months are considered to last 30 days and hence a full year has 360 days.
| Package | Function | Variant |
|---|---|---|
| Apache OpenOffice, Collabora Online, LibreOffice and Microsoft Excel | DAYS360 | NASD, but not SIA-compliant[15][16][17] |
| European | ||
| YEARFRAC | NASD and European | |
| SQL Server 2000 Analysis Services | Days360 | |
| Mathworks Financial Toolbox | days360 | US/NASD |
| days360e | European | |
| days360isda | ISDA | |
| days360psa | PSA | |
| Gnumeric | DAYS360 | |
| Apple Numbers | DAYS360 | NASD and European |
| YEARFRAC | NASD and European |
See also
- 365-day calendar, another accounting calendar with fixed year length
- Day count convention, standards for counting days
- French Republican Calendar, a calendar with twelve 30-day months and five or six appended holidays
- Iranian calendars, where the Old Persian calendar had 360 days with an extra month added every 6 years
References
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite webШаблон:Cbignore
- ↑ Шаблон:Cite web
- ↑ ISMA book “Bond Markets: Structures and Yield Calculations”, Шаблон:ISBN, and ISMA’s Circular 14 of 1997
- ↑ 2006 ISDA Definitions, Sec. 4.16 (g)
- ↑ 10,0 10,1 10,2 10,3 Шаблон:Cite web
- ↑ 11,0 11,1 11,2 Шаблон:Cite web
- ↑ 12,0 12,1 12,2 12,3 Accrual & Discounting Conventions
- ↑ Standard Securities Calculation Methods, Fixed Income Securities Formulas for Price, Yield, and Accrued Interest: Volume 1, 1993, Jan Mayle, New York, NY: Securities Industry Association, Шаблон:ISBN
- ↑ 2006 ISDA Definitions, Sec. 4.16 (f)
- ↑ See Microsoft Kb Article 916004. This bug is present in Excel versions 97 through 2007. This can be demonstrated by evaluating
DAYS360(DATE(2006,2,28), DATE(2007,2,28)); here years starting and ending on the last day in February only have 358 days. - ↑ OpenOffice is also not SIA-compliant, to maintain Excel compatibility see Issue 84934 — ODFF: DAYS360 compliance
- ↑ OpenOffice Documentation
