Daylight Saving Time
Daylight saving time, often called DST, is when some places move clocks forward for part of the year and move them back later.
At a glance
| Also called | DST or summer time. |
|---|---|
| Common effect | The local UTC offset changes by one hour. |
| Check with | world cities, IANA time zones, and the time zone converter. |
What daylight saving time changes
DST changes the relationship between local time and UTC. The clock may show the same morning routine, but the offset behind it changes.
Spring forward and fall back
Many places move clocks forward in spring and back in autumn. The exact dates depend on the country, region, and local law.
- A 2:00 AM hour may be skipped when clocks move forward.
- One hour may repeat when clocks move back.
- Not every country observes DST.
DST affects meetings and reminders
If you schedule with someone in another country, check both cities close to the event date. The time zone converter is safer than counting hours by hand.
How Alarm.now handles DST
The site uses time-zone data to show the active local time and offset.
City and IANA pages use current rules
A city clock uses the matching IANA time zone, so it can show whether the place is currently on standard time or daylight time.
- Open the city page for the human location.
- Open the IANA page for the technical time-zone identity.
- Open the UTC offset page to compare places sharing the same offset now.
Set reminders after checking the time
After you confirm the right local time, use the online alarm clock or online timer to turn that time into a reminder.
Related tools and guides
Frequently asked questions
Does every country use daylight saving time?
No. Some countries use it, some never use it, and some have changed their rules over time.
Why does my time difference change?
The difference changes when one place moves into or out of daylight saving time and the other place does not change on the same date.
How do I avoid DST mistakes?
Use a city or IANA time-zone page for the event date instead of adding or subtracting hours manually.