true if zones are equivalent at the specified time
// Same zone, different formats
equivalentZones("UTC+5", "UTC+05:00") // true
equivalentZones("UTC-8", -480) // true (480 minutes = 8 hours)
equivalentZones("GMT", "UTC") // true
equivalentZones("Z", 0) // true
// IANA zones matched by current offset (default behavior)
equivalentZones("America/New_York", "UTC-5") // true in winter (EST)
equivalentZones("America/New_York", "UTC-4") // true in summer (EDT)
// IANA zones at specific times
const winter = new Date("2023-01-15").getTime()
const summer = new Date("2023-07-15").getTime()
equivalentZones("America/New_York", "UTC-5", winter) // true (EST)
equivalentZones("America/New_York", "UTC-4", winter) // false (not EDT in winter)
equivalentZones("America/New_York", "UTC-4", summer) // true (EDT)
equivalentZones("America/New_York", "UTC-5", summer) // false (not EST in summer)
// Compare two IANA zones at a specific time
equivalentZones("America/New_York", "America/Toronto", winter) // true (both EST)
equivalentZones("America/New_York", "America/Los_Angeles", winter) // false (EST vs PST)
// Different zones
equivalentZones("UTC+8", "UTC+9") // false
// Invalid zones return false
equivalentZones("invalid", "UTC") // false
equivalentZones(null, "UTC") // false
Check if two timezone values are equivalent at a specific point in time.
Two zones are considered equivalent if they:
This is useful for:
For IANA zones with DST, you can specify a timestamp to evaluate equivalence at that moment. This is important when comparing historical records or future events where DST transitions matter.