diff --git a/generate/csdown/csharp_prefix.md b/generate/csdown/csharp_prefix.md
index a041ba73..b2dd2613 100644
--- a/generate/csdown/csharp_prefix.md
+++ b/generate/csdown/csharp_prefix.md
@@ -122,15 +122,16 @@ To get started quickly, here are some [examples](../../demo/csharp/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/generate/hydrogen/c_prefix.md b/generate/hydrogen/c_prefix.md
index 1ae15eb3..7ef57899 100644
--- a/generate/hydrogen/c_prefix.md
+++ b/generate/hydrogen/c_prefix.md
@@ -138,15 +138,16 @@ To get started quickly, here are some [examples](../../demo/c/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/generate/jsdoc2md/js.hbs b/generate/jsdoc2md/js.hbs
index 84ca1406..1c59fc45 100644
--- a/generate/jsdoc2md/js.hbs
+++ b/generate/jsdoc2md/js.hbs
@@ -118,15 +118,16 @@ and some [Node.js examples](../../demo/nodejs/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/generate/kotlindoc/kotlin_prefix.md b/generate/kotlindoc/kotlin_prefix.md
index 896fd135..4ae331fe 100644
--- a/generate/kotlindoc/kotlin_prefix.md
+++ b/generate/kotlindoc/kotlin_prefix.md
@@ -46,15 +46,16 @@ For other build tools support have a look at [this](https://jitpack.io/#cosineki
 <a name="coords"></a>
 ## Coordinate Transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/generate/pydown/py_prefix.md b/generate/pydown/py_prefix.md
index f54147ff..fd5c5289 100644
--- a/generate/pydown/py_prefix.md
+++ b/generate/pydown/py_prefix.md
@@ -135,15 +135,16 @@ To get started quickly, here are some [examples](../../demo/python/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/source/c/README.md b/source/c/README.md
index 2f2a4dd1..f73f7c0c 100644
--- a/source/c/README.md
+++ b/source/c/README.md
@@ -138,15 +138,16 @@ To get started quickly, here are some [examples](../../demo/c/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/source/csharp/README.md b/source/csharp/README.md
index cca059ce..72779395 100644
--- a/source/csharp/README.md
+++ b/source/csharp/README.md
@@ -122,15 +122,16 @@ To get started quickly, here are some [examples](../../demo/csharp/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/source/js/README.md b/source/js/README.md
index 66f83971..11bf0749 100644
--- a/source/js/README.md
+++ b/source/js/README.md
@@ -118,15 +118,16 @@ and some [Node.js examples](../../demo/nodejs/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/source/kotlin/README.md b/source/kotlin/README.md
index 0593c4c6..86ba927c 100644
--- a/source/kotlin/README.md
+++ b/source/kotlin/README.md
@@ -46,15 +46,16 @@ For other build tools support have a look at [this](https://jitpack.io/#cosineki
 <a name="coords"></a>
 ## Coordinate Transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.
 
diff --git a/source/python/README.md b/source/python/README.md
index c8f3c0d6..47e36172 100644
--- a/source/python/README.md
+++ b/source/python/README.md
@@ -135,15 +135,16 @@ To get started quickly, here are some [examples](../../demo/python/).
 
 ### Coordinate transforms
 
-The following five orientation systems are supported.
+The following orientation systems are supported.
 Astronomy Engine can convert a vector from any of these orientations to any of the others.
 It also allows converting from a vector to spherical (angular) coordinates and back,
 within a given orientation. Note the 3-letter codes for each of the orientation systems;
 these are used in function and type names.
 
 - **EQJ = Equatorial J2000**: Uses the Earth's equator on January 1, 2000, at noon UTC.
-- **EQD = Equator of-date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
-- **ECL = Ecliptic**: Uses the mean plane of the Earth's orbit around the Sun. The x-axis is referenced against the J2000 equinox.
+- **EQD = Equator of Date**: Uses the Earth's equator on a given date and time, adjusted for precession and nutation.
+- **ECT = True Ecliptic of Date**: Uses the true orbital plane and equator of the Earth on the given date.
+- **ECL = Mean J2000 Ecliptic**: Uses the plane of the Earth's orbit around the Sun in the year 2000. The x-axis is referenced against the J2000 mean equinox.
 - **HOR = Horizontal**: Uses the viewpoint of an observer at a specific location on the Earth at a given date and time.
 - **GAL = Galactic**: Based on the IAU 1958 definition of galactic coordinates.