I had an opportunity to research daylight saving time (summer time) again, so I’ll share what I found.

By the way, I didn’t immediately understand what DST meant, but apparently in America they use the expression “daylight saving time (DST)”. Summer time is British English.

summer time vs daylight saving time (DST)

The terms summer time and DST seem to vary by country and region.

• Summer time (British: summer time, also used in continental Europe)
• Daylight saving time (American: daylight saving time (DST), also used in Canada and Australia)

On the start date, 2:00 AM becomes 3:00 AM, and on the end date, 2:00 AM becomes 1:00 AM, making the start date 23 hours long and the end date 25 hours long.

• 夏時間 - Wikipedia

PST → PDT Switching Time

The timing for switching from Pacific Standard Time (PST) to Pacific Daylight Time (PDT) occurs at 2:00 AM becomes 3:00 AM in local time.

This timing is supposedly set at 2:00 AM because that’s when restaurants and other businesses typically close.

PDT → PST Switching Time

In the reverse pattern, when switching from PDT to PST, it occurs at 2:00 AM becomes 1:00 AM in local time.

Summary of Daylight Saving Time Specifications

When developing services for the American market, I think you need to implement systems considering daylight saving time, so I recommend understanding the specifications including the switching times.

That’s all from the Gemba.