"tan ddydd Sul y pys" meaning in Welsh

{
  "etymology_templates": [
    {
      "args": {
        "1": "until the peas' Sunday"
      },
      "expansion": "“until the peas' Sunday”",
      "name": "m-g"
    },
    {
      "args": {
        "1": "until the peas' Sunday"
      },
      "expansion": "Literally, “until the peas' Sunday”",
      "name": "lit"
    }
  ],
  "etymology_text": "Literally, “until the peas' Sunday”.",
  "head_templates": [
    {
      "args": {
        "1": "cy",
        "2": "phrase",
        "head": "tan ddydd Sul y pys"
      },
      "expansion": "tan ddydd Sul y pys",
      "name": "head"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Welsh entries with incorrect language header",
          "parents": [],
          "source": "w"
        }
      ],
      "glosses": [
        "when pigs fly, when two Sundays come together, never"
      ],
      "id": "en-tan_ddydd_Sul_y_pys-cy-phrase-F~S9xSQP",
      "links": [
        [
          "when pigs fly",
          "when pigs fly"
        ],
        [
          "when two Sundays come together",
          "when two Sundays come together"
        ],
        [
          "never",
          "never"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) when pigs fly, when two Sundays come together, never"
      ],
      "related": [
        {
          "english": "to herd cats; to eat porridge with an awl",
          "tags": [
            "literally"
          ],
          "translation": "to herd cats; to eat porridge with an awl",
          "word": "bwyta uwd â mynawyd"
        },
        {
          "english": "when Christmas will be in the summer and goosberries in winter",
          "tags": [
            "literally"
          ],
          "translation": "when Christmas will be in the summer and goosberries in winter",
          "word": "pan fydd Nadolig yn yr haf a gwsberis yn y gaeaf"
        },
        {
          "english": "when Hell freezes over",
          "translation": "when Hell freezes over",
          "word": "pan fydd uffern yn rhewi drosodd"
        },
        {
          "english": "when pigs fly; when Snowdon is made of cheese",
          "tags": [
            "literally"
          ],
          "translation": "when pigs fly; when Snowdon is made of cheese",
          "word": "pan fydd yr Wyddfa’n gaws"
        },
        {
          "english": "once in a blue moon; once in the four seasons",
          "tags": [
            "literally"
          ],
          "translation": "once in a blue moon; once in the four seasons",
          "word": "unwaith yn y pedwar amser"
        },
        {
          "english": "once in a blue moon; once in the four winds",
          "tags": [
            "literally"
          ],
          "translation": "once in a blue moon; once in the four winds",
          "word": "unwaith yn y pedwar gwynt"
        }
      ],
      "tags": [
        "idiomatic"
      ]
    }
  ],
  "word": "tan ddydd Sul y pys"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "until the peas' Sunday"
      },
      "expansion": "“until the peas' Sunday”",
      "name": "m-g"
    },
    {
      "args": {
        "1": "until the peas' Sunday"
      },
      "expansion": "Literally, “until the peas' Sunday”",
      "name": "lit"
    }
  ],
  "etymology_text": "Literally, “until the peas' Sunday”.",
  "head_templates": [
    {
      "args": {
        "1": "cy",
        "2": "phrase",
        "head": "tan ddydd Sul y pys"
      },
      "expansion": "tan ddydd Sul y pys",
      "name": "head"
    }
  ],
  "lang": "Welsh",
  "lang_code": "cy",
  "pos": "phrase",
  "related": [
    {
      "english": "to herd cats; to eat porridge with an awl",
      "tags": [
        "literally"
      ],
      "translation": "to herd cats; to eat porridge with an awl",
      "word": "bwyta uwd â mynawyd"
    },
    {
      "english": "when Christmas will be in the summer and goosberries in winter",
      "tags": [
        "literally"
      ],
      "translation": "when Christmas will be in the summer and goosberries in winter",
      "word": "pan fydd Nadolig yn yr haf a gwsberis yn y gaeaf"
    },
    {
      "english": "when Hell freezes over",
      "translation": "when Hell freezes over",
      "word": "pan fydd uffern yn rhewi drosodd"
    },
    {
      "english": "when pigs fly; when Snowdon is made of cheese",
      "tags": [
        "literally"
      ],
      "translation": "when pigs fly; when Snowdon is made of cheese",
      "word": "pan fydd yr Wyddfa’n gaws"
    },
    {
      "english": "once in a blue moon; once in the four seasons",
      "tags": [
        "literally"
      ],
      "translation": "once in a blue moon; once in the four seasons",
      "word": "unwaith yn y pedwar amser"
    },
    {
      "english": "once in a blue moon; once in the four winds",
      "tags": [
        "literally"
      ],
      "translation": "once in a blue moon; once in the four winds",
      "word": "unwaith yn y pedwar gwynt"
    }
  ],
  "senses": [
    {
      "categories": [
        "Pages with 1 entry",
        "Pages with entries",
        "Welsh entries with incorrect language header",
        "Welsh idioms",
        "Welsh lemmas",
        "Welsh multiword terms",
        "Welsh phrases"
      ],
      "glosses": [
        "when pigs fly, when two Sundays come together, never"
      ],
      "links": [
        [
          "when pigs fly",
          "when pigs fly"
        ],
        [
          "when two Sundays come together",
          "when two Sundays come together"
        ],
        [
          "never",
          "never"
        ]
      ],
      "raw_glosses": [
        "(idiomatic) when pigs fly, when two Sundays come together, never"
      ],
      "tags": [
        "idiomatic"
      ]
    }
  ],
  "word": "tan ddydd Sul y pys"
}