The first date as a Date object or timestamp (number)
The second date as a Date object or timestamp (number)
The difference in complete hours (negative if dateLeft is before dateRight), or NaN if any input is invalid
// Basic hour difference
const result = diffHours(new Date(2024, 5, 15, 14, 30), new Date(2024, 5, 15, 12, 0));
// Returns: 2
// Minutes/seconds are ignored (same hour)
const result = diffHours(new Date(2024, 5, 15, 14, 59), new Date(2024, 5, 15, 14, 0));
// Returns: 0
// Works with timestamps
const timestamp1 = new Date(2024, 5, 15, 16, 0).getTime();
const timestamp2 = new Date(2024, 5, 15, 14, 0).getTime();
const result = diffHours(timestamp1, timestamp2);
// Returns: 2
// Negative result when first date is earlier
const result = diffHours(new Date(2024, 5, 15, 10, 30), new Date(2024, 5, 15, 14, 30));
// Returns: -4
// Invalid inputs return NaN
const result = diffHours(new Date("invalid"), new Date(2024, 5, 15, 14, 0));
// Returns: NaN
Calculate the difference in complete hours between two dates.
This function calculates the number of complete hours between two dates by comparing them at the start of each hour. Minutes, seconds, and milliseconds are ignored to ensure accurate hour counting.