curl --request GET \
  --url https://openapi.fcontext.com/api/market-data/market/trading_days \
  --header 'x-api-key: <api-key>'

{
  "days": {
    "tradingDays": [
      "2023-12-25"
    ],
    "halfTradingDays": [
      "2023-12-25"
    ]
  }
}