Original sentence: If the position of the earth (or the sun) is reckoned with respect to the equinox, then the dates indicate the season (and so is synchronized to the declination of the sun).The mean calendar year of such a calendar approximates some form of the tropical year (typically either the mean tropical year or the vernal equinox year)
Edited sentence: If the position of the earth (in its orbit around the sun) is reckoned with respect to the equinox (the point at which the earth's orbit crosses the celestial equator), then the dates accurately indicate the season, that is, they are synchronized with the declination of the sun.The mean calendar year of such a calendar approximates some form of the tropical year, usally either the mean tropical year or the vernal equinox year