"calendar method" meaning in English

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      "name": "en-noun"
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  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
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        {
          "kind": "topical",
          "langcode": "en",
          "name": "Birth control",
          "orig": "en:Birth control",
          "parents": [
            "Pregnancy",
            "Sex",
            "Body",
            "Gynaecology",
            "All topics",
            "Reproduction",
            "Female",
            "Medicine",
            "Fundamental",
            "Life",
            "Gender",
            "Biology",
            "Healthcare",
            "Nature",
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      "glosses": [
        "A rhythm method of natural birth control."
      ],
      "id": "en-calendar_method-en-noun-8PGWSkxY",
      "links": [
        [
          "rhythm method",
          "rhythm method"
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          "birth control",
          "birth control"
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      ]
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  "word": "calendar method"
}

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  "lang_code": "en",
  "pos": "noun",
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        "en:Birth control"
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      "glosses": [
        "A rhythm method of natural birth control."
      ],
      "links": [
        [
          "rhythm method",
          "rhythm method"
        ],
        [
          "birth control",
          "birth control"
        ]
      ]
    }
  ],
  "word": "calendar method"
}