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    Function subDays

    • Subtract the specified number of days from the given date.

      This function validates arguments before processing and returns a new Date instance with the specified number of days subtracted. Fractional days are truncated toward zero.

      Parameters

      • date: number | Date

        The base date as a Date object or timestamp (number)

      • amount: number

        The number of days to subtract (can be negative to add)

      Returns Date

      A new Date object with the days subtracted, or Invalid Date if any input is invalid

      // Subtract positive days
      const result = subDays(new Date(2025, 0, 10), 5);
      // Returns: 2025-01-05

      // Add days (negative amount)
      const result = subDays(new Date(2025, 0, 10), -3);
      // Returns: 2025-01-13

      // Works with timestamps
      const timestamp = Date.now();
      const result = subDays(timestamp, 7);
      // Returns: Date 7 days ago from now

      // Fractional amounts are truncated
      const result = subDays(new Date(2025, 0, 5), 1.9);
      // Returns: 2025-01-04 (1.9 truncated to 1)

      // Invalid inputs return Invalid Date
      const result = subDays(new Date("invalid"), 5);
      // Returns: Invalid Date

      const result = subDays(new Date(2025, 0, 1), NaN);
      // Returns: Invalid Date
      • Validates arguments before conversion (consistent with library patterns)
      • Accepts both Date objects and numeric timestamps
      • Fractions are truncated using Math.trunc (1.9 → 1, -1.9 → -1)
      • Returns Invalid Date for: Invalid Date, NaN, Infinity, -Infinity
      • Always returns a new Date instance (does not mutate input)

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