The Tree/Ogam dates, as formulated according to Charles's tree-leap rule, follow a 76-year cycle, except when the Gregorian calendar drops a leap day. One need only know whether the tree date is a day early compared to standard conversion to the Gregorian calendar to work out the correct tree date. Then one can use the Ogam wheel to work out the moon phase rune.

In the 76-year cycle, when a leap day is dropped from the Gregorian calendar as in 1900, 2100, 2200 etc, the corresponding period when tree-dates a day early is also dropped.

The dates below are the Gregorian dates for which the tree calendar dates are a day early. Each of these 19 periods begins with a Gregorian leap day and ends with the zero day of a tree month in which a sacrifice is cancelled. I then give the Tree/Ogam date of the cancelled sacrifice, which is either the zero day or the day after and also its Golden number.

76-year cycle 1989-2064 :

1992-02-29 - 1992-11-24 R1u+ G#8 1996-02-29 - 1997-09-01 M1u+ G#13 2000-02-29 - 2002-05-12 H0u+ G#18 2004-02-29 - 2005-07-07 T0u+ G#2 2008-02-29 - 2010-05-12 H1u+ G#7 2012-02-29 - 2013-07-07 T1u+ G#10 2016-02-29 - 2016-09-01 M1u+ G#13 2020-02-29 - 2021-05-12 H0u+ G#18 2024-02-29 - 2024-07-07 T0u+ G#2 2028-02-29 - 2029-05-12 H1u+ G#7 2032-02-29 - 2032-07-07 T1u+ G#10 2036-02-29 - 2037-03-17 F0u+ G#15 2040-02-29 - 2040-05-12 H0u+ G#18 2044-02-29 - 2045-03-17 F1u+ G#4 2048-02-29 - 2048-05-12 H1u+ G#7 2052-02-29 - 2054-09-01 M1u+ G#13 2056-02-29 - 2056-03-17 F0u+ G#15 2060-02-29 - 2060-11-24 R0u+ G#19 2064-02-29 - 2064-03-17 F1u+ G#4

The cancelled sacrifices can be identified by their golden numbers, so this table can be made compact by using just the golden numbers. Then one gets:

8-8, 12-13, 16-18, 1-2. 5-7, 9-10, 13-13, 17-18, 2-2. 6-7, 10-10, 14-15, 18-18, 3-4. 7-7, 11-13, 15-15, 19-19, 4-4.Here we see the 9 different cancelled sacrifices and the years of the 76-year cycle (1989-2064) that use them:

T0u+ G#2 2005, 2024. F1u+ G#4 2045, 2064. H1u+ G#7 2010, 2029, 2048. R1u+ G#8 1992. T1u+ G#10 2013, 2032 M1u+ G#13 2054, 1997, 2016. F0u+ G#15 2037, 2056. H0u+ G#18 2002, 2021, 2040. R0u+ G#19 2060.Sorted by time of year we get

F0u+ G#15 2037, 2056. F1u+ G#4 2045, 2064. -------------------------- H0u+ G#18 2002, 2021, 2040. H1u+ G#7 2010, 2029, 2048. -------------------------- T0u+ G#2 2005, 2024. T1u+ G#10 2013, 2032 -------------------------- M1u+ G#13 2054, 1997, 2016. -------------------------- R0u+ G#19 2060. R1u+ G#8 1992. --------------------------