The first date as a Date object or timestamp (number)
The second date as a Date object or timestamp (number)
The difference in milliseconds (negative if dateLeft is before dateRight), or NaN if any input is invalid
// Basic millisecond difference
const result = diffMilliseconds(new Date(2024, 5, 15, 14, 30, 45, 500), new Date(2024, 5, 15, 14, 30, 45, 100));
// Returns: 400
// Exact same time returns 0
const result = diffMilliseconds(new Date(2024, 5, 15, 14, 30, 45, 123), new Date(2024, 5, 15, 14, 30, 45, 123));
// Returns: 0
// Works with timestamps
const timestamp1 = new Date(2024, 5, 15, 14, 30, 46, 0).getTime();
const timestamp2 = new Date(2024, 5, 15, 14, 30, 45, 0).getTime();
const result = diffMilliseconds(timestamp1, timestamp2);
// Returns: 1000
// Negative result when first date is earlier
const result = diffMilliseconds(new Date(2024, 5, 15, 14, 30, 45, 100), new Date(2024, 5, 15, 14, 30, 45, 500));
// Returns: -400
// Invalid inputs return NaN
const result = diffMilliseconds(new Date("invalid"), new Date(2024, 5, 15, 14, 30, 45, 0));
// Returns: NaN
Calculate the difference in milliseconds between two dates.
This function calculates the exact difference in milliseconds between two dates. This is the most precise time difference calculation available, equivalent to subtracting the results of getTime().