Solar terms, also known as Chinese solar terms, are a traditional method of dividing the year into 24 segments based on the Sun’s position in the celestial sphere. Each solar term represents a specific time of year and is used to track agricultural activities and seasonal changes. When discussing solar terms in English, the prepositions “on” and “in” can be used, but their appropriateness depends on the context.

When to Use “On”

  1. Specific Date: If you are referring to a specific date that falls within a solar term, use “on.” For example:

    • “The summer solstice is on June 21st.”
    • “The winter solstice is on December 21st.”

  2. Exact Time: When mentioning the exact time of a solar term, “on” is also appropriate. For example:

    • “The sun reaches its highest point on the celestial equator on the summer solstice.”
    • “The winter solstice occurs on the shortest day of the year, on December 21st.”

  3. Traditional Celebrations: When discussing traditional festivals that are tied to solar terms, “on” is used. For example:

    • “Lantern Festival is celebrated on the 15th day of the first lunar month, on the solar term of the Grain in Ear.”

When to Use “In”

  1. General Time Frame: When referring to a general time frame that spans multiple days within a solar term, use “in.” For example:

    • “Spring begins in the solar term of the Beginning of Spring.”
    • “The Dog Days of Summer are in the solar term of the Heat.”

  2. Seasonal Changes: When describing the onset of a season, “in” is often used. For example:

    • “The season of summer is in the solar term of the Grain in Ear.”
    • “Autumn arrives in the solar term of the White Dew.”

  3. Duration: When indicating the duration of a solar term, “in” can be used. For example:

    • “The solar term of the Beginning of Summer lasts for about 15 days.”
    • “The solar term of the Cold Dew is in the middle of autumn.”

Examples

Here are some examples to illustrate the use of “on” and “in” with solar terms:

  • On: “This year, the Dragon Boat Festival falls on the 5th day of the 5th lunar month, on the solar term of the Grain in Ear.”
  • In: “The Mid-Autumn Festival is celebrated in the solar term of the Autumn Equinox, typically in September or October.”
  • On: “The day of the winter solstice is on December 21st, marking the shortest day of the year.”
  • In: “The solar term of the Greater Cold is in the middle of winter, from January 5th to January 20th.”

By understanding when to use “on” and “in,” you can effectively communicate about solar terms in English, whether you’re discussing a specific date, a general time frame, or seasonal changes.