Understanding Daylight Saving Time: A Complete Guide

Daylight Saving Time is the reason your recurring Monday meeting with London suddenly happens an hour later. Or earlier. Depending on whether you're in the US or Europe and what month it is.

It's confusing. Let me break it down.

What Is DST, Really?

Daylight Saving Time is the practice of moving clocks forward one hour during warmer months. The idea: more daylight in the evening when people are actually awake to use it.

Most places that observe it "spring forward" in March or April (clocks move ahead one hour) and "fall back" in October or November (clocks move back one hour).

The phrase to remember: "Spring forward, fall back."

In spring, 2 AM becomes 3 AM. You lose an hour of sleep. In fall, 2 AM becomes 1 AM again. You gain an hour.

Who Actually Does This?

Not everyone. And that's where coordination gets messy.

Countries That Observe DST

• Most of the United States and Canada (exceptions: Arizona, Hawaii, Saskatchewan)
• Most of Europe (all EU countries plus UK, Switzerland, Norway)
• Parts of Australia (New South Wales, Victoria, South Australia, Tasmania, ACT)
• New Zealand
• Some Middle Eastern countries (Israel, Palestine, parts of Lebanon)
• Small parts of South America (southern Chile, parts of Paraguay)

Countries That Don't

• Most of Asia: China, Japan, India, Indonesia, Thailand, Vietnam, Philippines
• Most of Africa: All countries except a few northern ones
• Most of South America: Brazil, Argentina (they stopped), Colombia, Peru
• Russia: Stopped in 2014
• Parts of US: Arizona (except Navajo Nation), Hawaii
• Parts of Australia: Queensland, Northern Territory, Western Australia

According to timeanddate.com's DST research, less than 40% of countries worldwide observe DST. Most of Asia and Africa don't bother.

When Do the Changes Happen?

Here's where it gets annoying for global teams: different regions change on different dates.

United States

• Spring forward: 2 AM on the second Sunday of March
• Fall back: 2 AM on the first Sunday of November

For 2026: March 8 and November 1

European Union

• Spring forward: 1 AM UTC on the last Sunday of March
• Fall back: 1 AM UTC on the last Sunday of October

For 2026: March 29 and October 25

Australia

Southern hemisphere, so seasons are flipped:

• Spring forward: 2 AM on the first Sunday of October
• Fall back: 2 AM/3 AM on the first Sunday of April

For 2026: October 4, 2026 and April 5, 2026

Notice the problem? The US and Europe don't change on the same dates. This creates "twilight periods" twice a year.

The Twilight Zone Problem

For a few weeks twice yearly, the time difference between regions temporarily changes.

Example: New York and London

Normally: 5 hours apart

Spring transition 2026:

• March 8: US springs forward (Europe hasn't yet)
• March 29: Europe springs forward
• During those 3 weeks: Only 4 hours apart instead of 5

Fall transition 2026:

• October 25: Europe falls back (US hasn't yet)
• November 1: US falls back
• During that week: Only 4 hours apart instead of 5

Your recurring meeting at 3 PM London / 10 AM New York will suddenly be 3 PM London / 11 AM New York during these periods.

If you're manually tracking meeting times instead of using timezone-aware tools, this will absolutely screw you up.

How DST Breaks Your Meetings

Recurring Meetings Shift

You set up a weekly standup at "10 AM New York time." Great.

Then DST happens. Now it's an hour different for your London team. They either show up at the wrong time, or you have to manually adjust the meeting.

If you use calendar tools properly (setting timezone when you create the event), this should auto-adjust. But if you just put "10 AM" without specifying timezone, chaos ensues.

Twice-Yearly Confusion

Every March and October/November, you'll get:

• People showing up an hour early or late
• Questions about "is the meeting still at the same time?"
• Confusion about whether "same time" means "same time on the clock" or "same time relative to UTC"

The week of a DST change, expect scheduling chaos unless you've proactively communicated.

Different Systems Handle It Differently

Google Calendar handles DST changes automatically if you set events with proper timezone info.

Apple Calendar sometimes gets confused if you're looking at events far in the future.

Outlook usually handles it correctly but requires events to be set with specific timezone.

Manually-entered calendar entries without timezone? Those don't adjust at all.

How to Handle DST in Scheduling

Use Timezone-Aware Tools

Tools like Whenest automatically calculate DST when you schedule meetings. You pick a future date, it shows the correct local times even if DST changes occur between now and then.

The meeting planner accounts for:

• Current DST status in each location
• Future DST transitions before your meeting date
• Locations that don't observe DST at all

Always Specify Timezone When Creating Events

When you create a calendar event, set the timezone explicitly. Don't just put "10 AM" — set "10 AM Eastern Time" or "10 AM GMT."

This tells the calendar system to adjust the event correctly when DST happens.

Communicate Around Transition Dates

Week before DST change: Send a reminder.

"Heads up: DST changes this weekend for US/Europe. Our Monday meeting time will shift by one hour for some of you. The meeting is still at 10 AM ET, which will now be 3 PM GMT instead of 2 PM GMT."

Make it explicit. Don't assume people will remember or figure it out.

Use UTC as a Reference

UTC (Coordinated Universal Time) never changes. It doesn't observe DST.

When documenting meeting times for reference, include the UTC time:

• "10 AM ET / 3 PM GMT / 1500 UTC"

This gives everyone an absolute reference point.

Check Future Times with Tools

If you're scheduling something three months out, don't assume you know the time difference. DST might change between now and then.

Use the time zone converter to check what the actual local times will be on that future date.

Best Practices for DST-Aware Teams

Set Up DST Alerts

Put recurring calendar reminders for yourself:

• Week before the second Sunday in March: "US DST coming"
• Week before the last Sunday in March: "EU DST coming"
• Week before the last Sunday in October: "EU DST coming"
• Week before the first Sunday in November: "US DST coming"

This prompts you to communicate with your team before confusion happens.

Document Meeting Times Clearly

In your team wiki or handbook, write:

• "Weekly standup: 10 AM Eastern Time / 3 PM UK time" (not just "10 AM")
• "Note: these local times may shift by an hour twice yearly due to DST transitions"

Test Your Calendar Setup

Create a test event six months in the future. Check how it displays for people in different time zones. Make sure your calendar system is actually handling DST correctly.

Don't Assume Time Differences

"London is 5 hours ahead of New York" is true most of the year. But not always.

Instead of memorizing time differences, use tools that calculate them dynamically based on current DST status.

Why DST Even Exists

The original idea: save energy by making better use of daylight.

The reality: it probably doesn't save energy anymore. Modern studies show minimal to no energy savings. According to Wikipedia's DST research, the energy savings are between 0-1% at best.

What DST does do:

• Disrupts sleep: Heart attacks increase the Monday after spring forward
• Confuses scheduling: As we've discussed extensively
• Annoys farmers: Contrary to popular belief, farmers generally oppose DST
• Causes car accidents: Drowsy driving increases after spring forward

The supposed benefits (more evening daylight for activities) are debatable.

The Future of DST

There's growing momentum to stop the twice-yearly clock changes.

European Union: Voted to abolish DST in 2019. Implementation delayed indefinitely because countries can't agree whether to stay on permanent summer time or permanent standard time.

United States: Various states have passed laws to adopt permanent DST, but federal law currently prevents this. Congress would need to approve (the Sunshine Protection Act has been proposed multiple times but not passed).

Other regions: Russia abolished DST in 2014. Turkey stopped in 2016. Several US states and territories don't observe it.

But until abolition actually happens globally, we're stuck with the twice-yearly confusion.

Practical Example

Let's say you're scheduling a recurring meeting for a US-Europe team:

Bad approach:

"Let's meet every Monday at 3 PM London time."

What happens: When DST changes, people in other timezones will be confused about whether the meeting moved or not.

Good approach:

"Let's meet every Monday at 3 PM London time / 10 AM New York time. Note that these local times will remain consistent, but the relationship between them will shift slightly during DST transitions. I'll send a reminder before each DST change."

Then use Whenest's meeting planner to generate a calendar invite that handles DST correctly.

See our How It Works guide for step-by-step instructions.

Bottom Line

DST is confusing, probably unnecessary, and creates genuine problems for global teams. But it's still here, so you need to handle it properly.

Key takeaways:

• Less than 40% of countries observe DST
• Those that do change on different dates
• This creates transition periods where time differences temporarily shift
• Use timezone-aware tools to handle it automatically
• Communicate proactively around DST transition dates
• Always specify timezone, never assume time differences

Want to stop worrying about DST? Use Whenest to automatically handle all timezone math including DST transitions. Or check our FAQ for more details on how we handle different scenarios.