The base date as a Date object or timestamp (number)
A new Date object with the same value, or Invalid Date if input is invalid
// No truncation (millisecond is smallest unit)
const result = truncMillisecond(new Date(2024, 5, 15, 14, 30, 45, 123));
// Returns: June 15, 2024 14:30:45.123 (unchanged)
// Returns new object with same value
const result2 = truncMillisecond(new Date(2024, 11, 31, 23, 59, 59, 999));
// Returns: December 31, 2024 23:59:59.999 (unchanged)
// Works with timestamps
const timestamp = Date.now();
const result3 = truncMillisecond(timestamp);
// Returns: Date with same timestamp value
// Unix epoch
const result4 = truncMillisecond(new Date(0));
// Returns: January 1, 1970 00:00:00.000
// Invalid inputs return Invalid Date
const result5 = truncMillisecond(new Date("invalid"));
// Returns: Invalid Date
Truncate a date to the millisecond.
This function returns the same date without any truncation since millisecond is the smallest unit supported by JavaScript Date objects. It is provided for API consistency with other truncation functions.