Daylight Saving Time: Why Your Market Hours “Move”

DST doesn't change the exchange's local schedule, but it can shift your local conversion and even change overlap windows for a few weeks.

The core idea

An exchange usually keeps the same local open/close schedule. What changes is how that schedule appears in your time zone when countries switch in and out of daylight saving time.

The "mismatch weeks" problem

Because DST start/end dates differ between regions, you can get short periods where overlaps change. For example, London and New York can have an extra hour of overlap during certain DST mismatch windows.

Why it matters

• Strategy timing: If your system trades "the first hour," that first hour may shift in your local time.
• Scheduling: Economic releases can suddenly land inside (or outside) your preferred trading window.
• Fewer mistakes: You don't want to find out a market is closed after you've planned your day.

Practical approach

• Always store exchange hours in the exchange's IANA time zone.
• Convert to the user's local time for display only.
• Show both "Local exchange time" and "Your time" on every detail page.