The year 2007 is the 13th year of the 19-year cycle, with epact 11.  Lunar year 2007 begins on December 21st, 2006 (that is, at sunset on December 20th, 2006), as can be seen by examining the table below at the intersection of the row for year 13 and the column for the first moon.

Lunar Months of the Gregorian Easter Cycle
Civil calendar date of the first day of the lunar month.  This table is valid for the years 1900-2199.
The almanac for other time periods is available:   1700-1899 ;   2200-2299 .

 
 
lunar month:
1
2
3
4
5
6
7
8
9
10
11
12
13
 
 
 
30 days
29 days (in some years, 30)
30 days
29 days
30 days
29 days
30 days
29 days
30 days
29 days
30 days
29 days (in year 2199, 30 days)
30 days (in 19th year, 29)
year of Gregorian cycle
year of Jewish cycle
epact
 
 
 
 
 
 
 
 
 
 
 
 
 
1
17
29
 2-Jan
 1-Feb
 2-Mar
 1-Apr
30-Apr
30-May
28-Jun
28-Jul
26-Aug
25-Sep
24-Oct
23-Nov
 
2
18
10
22-Dec
21-Jan
19-Feb
21-Mar
19-Apr
19-May
17-Jun
17-Jul
15-Aug
14-Sep
13-Oct
12-Nov
 
3
19
21
11-Dec
10-Jan
 8-Feb
10-Mar
 8-Apr
 8-May
 6-Jun
 6-Jul
 4-Aug
 3-Sep
 2-Oct
 1-Nov
30-Nov
4
1
2
30-Dec
29-Jan
27-Feb
29-Mar
27-Apr
27-May
25-Jun
25-Jul
23-Aug
22-Sep
21-Oct
20-Nov
 
5
2
13
19-Dec
18-Jan
16-Feb
18-Mar
16-Apr
16-May
14-Jun
14-Jul
12-Aug
11-Sep
10-Oct
 9-Nov
 
6
3
24
 8-Dec
 7-Jan
 5-Feb
 7-Mar
 5-Apr
 5-May
 3-Jun
 3-Jul
 1-Aug
31-Aug
29-Sep
29-Oct
27-Nov
7
4
5
27-Dec
26-Jan
24-Feb
26-Mar
24-Apr
24-May
22-Jun
22-Jul
20-Aug
19-Sep
18-Oct
17-Nov
 
8
5
16
16-Dec
15-Jan
13-Feb
15-Mar
13-Apr
13-May
11-Jun
11-Jul
 9-Aug
 8-Sep
 7-Oct
 6-Nov
 5-Dec
9
6
27
 4-Jan
 3-Feb
 4-Mar
 3-Apr
 2-May
 1-Jun
30-Jun
30-Jul
28-Aug
27-Sep
26-Oct
25-Nov
 
10
7
8
24-Dec
23-Jan
21-Feb
23-Mar
21-Apr
21-May
19-Jun
19-Jul
17-Aug
16-Sep
15-Oct
14-Nov
 
11
8
19
13-Dec
12-Jan
10-Feb
12-Mar
10-Apr
10-May
 8-Jun
 8-Jul
 6-Aug
 5-Sep
 4-Oct
 3-Nov
 2-Dec
12
9
30
 1-Jan
31-Jan
 1-Mar
31-Mar
29-Apr
29-May
27-Jun
27-Jul
25-Aug
24-Sep
23-Oct
22-Nov
 
13
10
11
21-Dec
20-Jan
18-Feb
20-Mar
18-Apr
18-May
16-Jun
16-Jul
14-Aug
13-Sep
12-Oct
11-Nov
 
14
11
22
10-Dec
 9-Jan
 7-Feb
 9-Mar
 7-Apr
 7-May
 5-Jun
 5-Jul
 3-Aug
 2-Sep
 1-Oct
31-Oct
29-Nov
15
12
3
29-Dec
28-Jan
26-Feb
28-Mar
26-Apr
26-May
24-Jun
24-Jul
22-Aug
21-Sep
20-Oct
19-Nov
 
16
13
14
18-Dec
17-Jan
15-Feb
17-Mar
15-Apr
15-May
13-Jun
13-Jul
11-Aug
10-Sep
 9-Oct
 8-Nov
 
17
14
25*
 7-Dec
 6-Jan
 4-Feb
 6-Mar
 4-Apr
 4-May
 2-Jun
 2-Jul
31-Jul
30-Aug
28-Sep
28-Oct
26-Nov
18
14
6
26-Dec
25-Jan
23-Feb
25-Mar
23-Apr
23-May
21-Jun
21-Jul
19-Aug
18-Sep
17-Oct
16-Nov
 
19
16
17
15-Dec
14-Jan
12-Feb
14-Mar
12-Apr
12-May
10-Jun
10-Jul
 8-Aug
 7-Sep
 6-Oct
 5-Nov
 4-Dec



 
 
 
 
 

How to use this table:

The year:

The Gregorian lunar almanac (also called the Gregorian "ecclesiastical moon") is a 19-year cycle which assigns an age of the moon to every day in the 19-year period.

Year one of the Gregorian cycle is any year in which the year's number is divisible by 19 without remainder.  The year 1995, for example, was year one of its cycle:  The table shows that Lunar Year 1995 began on January 2nd, 1995.  (More precisely, at sunset on January 1st, 1995).   Successive years of the cycle follow in order.  The year 1996 was year two:  Lunar Year 1996 began on December 22nd, 1995  (Or more precisely, at sunset on December 21st, 1995).   The year 1997 was year 3:  Lunar Year 1997 began on December 11th, 1996.
 

The month:

Each year contains 12 or 13 lunar months.  Each lunar month has formally 29 or 30 days.   The table above shows the first day of each lunar month in the Gregorian Easter cycle.  The moon is considered to be one day old on the first day of the lunar month.  This day is also called "new moon" because it corresponds, on the average, to the day on which the new waxing  crescent moon theoretically first becomes visible.

Although each lunar month contains formally either 29 or 30 days, in the Gregorian lunar almanac the actual number of days assigned to a given lunation might be as few as 28  (when the almanac assigns lunar ages differing by 2 to successive days in a month formally having 29 days) and as many as 31 (when the almanac assigns the same lunar age to successive days in a month formally having 30 days).  If one simply uses the starting dates listed in the table above, these complications will be taken care of automatically. However, if one wishes to use the Gregorian lunar almanac not just as an almanac, but as a calendar, in which every day is designated by a unique and unambiguous date, additional rules may be needed, such as the rules enumerated below for February 29th, for the 13th moon of the 19th year of the cycle, and for the 12th moon of the year 2199.
 
 
 

Transition from Almanac to Calendar--Additional Rules:

These additional rules are used to adjust the Gregorian lunar almanac to conform to the following constraints:  (1)  Every lunar month will have exactly 29 or 30 days numbered consecutively; (2) each day is uniquely identified by the number of the year, the  number of the month, and the number of the day; no day does double duty as the last day of the outgoing month and the first day of the incoming month;  (3) the number of variable months, which can have either 29 or 30 days, is to be no more than 4.  The approach taken here is to designate months 2, 11, 12, and 13 as variable.  This allows any year of 12 months to be reduced in length by a day, and any year of 13 months to be reduced in length by as much as two days, and any year, whether of 12 or 13 lunar months, to be increased in length by as much as two days,.  A more flexible approach would designate months 2, 9, 11, and 12 as variable, allowing any year whatsoever to be reduced or extended by as much as two days. It will be centuries before this additional flexibility is needed,  however, so the table above follows the traditional approach of making the 13th month variable.

The additional rules themselves are subject to the constraint that the Gregorian lunar calendar (almanac plus additional rules) must set the Easter holiday to the same date as the unadjusted Gregorian lunar almanac.

Additional Rule 1:  If February has 29 days, an extra day is added to lunar month 2, making it a month of 30 days, rather than 29 days.  Month 3 then begins a day later than the date listed in the table if the date listed is a date prior to February 29th.  (The unadjusted almanac compensates for February 29th by declaring the moon's age on February 29th to be the same as her age February 28th; or, in the alternative, by declaring the moon's age on February 25th to be the same as her age on February 24th in a bissextile year.)

Additional Rule 2:  The thirteenth lunar month of the 19th year of the cycle has 29 days in the years 1900-2199.  (Though this saltus lunae or moon's jump is already part of the unadjusted almanac, this rule is added to ensure that the days will be numbered consecutively.)

Additional Rule 3: In the year 2199, which is the 15th year of the 19-year cycle and the last year in which this table is valid, an extra day is added to lunar month 12, making it a month of 30 days, rather than 29 days.  (The unadjusted lunar almanac manages the transition from the year 2199 to the year 2200 by setting the moon's age on January 1st, 2200 to be the same as her age on December 31st, 2199.)
 

The day:

Because this is a Babylonian-style lunar calendar, the day begins on sunset of the day prior to the day listed in the table.  The table shows that the first day of the first moon of year 1 of the cycle corresponds to January 2nd.  This means that the first day  of the lunar month begins at sunset on January 1st and ends at sunset on January 2nd, when the second day of the lunar month begins.
 

The Easter festival falls in the first lunar month of the year to begin on or after March 8th.  This is usually the 4th moon, though in years 6 and 17  of the 19-year cycle it is the 5th moon.  Easter is always the third Sunday in its lunar month.

In the Earth's Northern hemisphere, the Spring season of year 4 of the Gregorian cycle coincides with the Spring season of year 1 of the Jewish 19-year cycle, with other years of each cycle following in succession.  The Feast of Unleavened Bread for the year 5754 (year 16 of the Jewish cycle) came in the Northern hemisphere's springtime in the Gregorian year 1994 (year 19 of the Gregorian cycle.)

Due to differences in the time of year at which the Christian and Jewish cycles add the 13th moon of 13-moon years, the Jewish Feast of Unleavened Bread will, in years 3, 11, and 14 of the Gregorian cycle (corresponding respectively to years 19, 8, and 11 of the Jewish cycle), fall in the lunar month next after the lunar month in which the Christian Easter festival falls.  In all other years of the cycle, Easter and the Feast of Unleavened Bread fall in the same lunar month.  But though the lunar month in which the Jewish Feast of Unleavened Bread falls can be identified using the table above, the precise dates of the Feast of Unleavened Bread cannot be determined accurately from the table.  This is because the Gregorian and Jewish calendars use different rules for computing the moon's age.



 

References:

Explanatory Supplement to the Ephemeris and the American Ephemeris and Nautical Almanac, H. M. Stationery Office, London, 1966, fourth revised printing, 1977.

Alexander Philip, The Calendar: Its History, Structure and Improvement, University Press, Cambridge, 1921.

L. A. Resnikoff, "Jewish Calendar Calculations I", Scripta Mathematica 9, 191(1943); "Jewish Calendar Calculations II", Scripta Mathematica 9, 274(1943).