EST vs EDT, PST vs PDT: Why the Abbreviation Changes in Summer
EST and PST are fixed standard-time offsets. New York and Los Angeles switch to EDT and PDT during daylight saving time. Use literal abbreviations for named offsets and city names for seasonal local time.
Quick Reference
| Abbr | Full Name | Offset | Active | Cities |
|---|---|---|---|---|
| EST | Eastern Standard Time | UTC−5 | Nov – Mar | New York, Toronto, Washington DC |
| EDT | Eastern Daylight Time | UTC−4 | Mar – Nov | Same cities — clocks sprung forward |
| PST | Pacific Standard Time | UTC−8 | Nov – Mar | Los Angeles, San Francisco, Seattle |
| PDT | Pacific Daylight Time | UTC−7 | Mar – Nov | Same cities — clocks sprung forward |
| GMT | Greenwich Mean Time | UTC±0 | Oct – Mar | London in winter |
| BST | British Summer Time | UTC+1 | Mar – Oct | London in summer |
EST vs EDT
EST (Eastern Standard Time) is UTC−5. It applies to US eastern states from the first Sunday of November through the second Sunday of March — roughly four months of the year in New York.
EDT (Eastern Daylight Time) is UTC−4. It applies during roughly the remaining eight months in New York, when clocks spring forward by one hour. New York, Boston, Toronto, Washington DC, and Miami all switch between EST and EDT on the same dates.
Many people use "EST" year-round as a shorthand, but saying "3 PM EST" in July technically means 3 PM UTC−5 — one hour behind where New York actually is. For scheduling, use "ET" (Eastern Time) if you want a label that is correct in all seasons, or use the IANA identifier America/New_York in any system that accepts it.
PST vs PDT
PST (Pacific Standard Time) is UTC−8, active from November through March in Los Angeles, San Francisco, Seattle, and Portland.
PDT (Pacific Daylight Time) is UTC−7, active March through November. The switch happens on the same dates as the eastern US. The EST–PST gap and the EDT–PDT gap are both three hours. New York and Los Angeles normally keep that gap, with brief exceptions during the different local changeover hours.
Like "ET" for the east coast, "PT" (Pacific Time) is the season-agnostic label that is always correct for the US west coast.
Fixed Offsets and City Times Answer Different Questions
EST = UTC−5, PST = UTC−8 and GMT = UTC+0 are correct definitions. A mistake arises when a fixed offset is substituted for a city that observes DST, or a city’s summer time is labelled with its standard-time abbreviation.
Two valid conversions with different meanings
- ✓Fixed-offset answer: 3 PM EST = 8 PM GMT (valid year-round for those named offsets)
- ✓IANA-based answer: 3 PM EDT = 8 PM BST (correct — both cities are on DST in June)
Both examples show 3 PM to 8 PM, but they refer to different instants. In June, 3 PM EST is 4 PM in New York, while 3 PM EDT is 3 PM in New York. The labels are part of the answer, not interchangeable decoration.
For city-time planning, New York and London have a four-hour gap during their spring and autumn DST mismatch periods, rather than the usual five hours. A literal EST-to-GMT conversion still has a five-hour gap because neither named offset changes.
TimezoneCast calculates city-time offsets using the IANA timezone database for the selected date. Fixed-abbreviation answers separately retain their stated UTC offsets.
GMT vs BST — The Same Problem for London
London follows the same pattern. GMT (Greenwich Mean Time) is UTC+0 and applies in winter. From late March through late October, the UK switches to BST (British Summer Time), which is UTC+1.
A converter that always shows London as GMT will be one hour behind the correct answer from late March through late October. The same logic applies: use city names and the intended date when you need seasonal local time. Use GMT explicitly when UTC+0 is intended.
The US–Europe Transition Windows
New York switches clocks on the second Sunday of March. London switches on the last Sunday of March — two or three weeks later. A similar gap occurs in fall: the EU switches on the last Sunday of October, the US on the first Sunday of November.
The spring mismatch lasts two or three weeks; the autumn mismatch lasts one week. During those periods, 10 AM New York corresponds to 2 PM London instead of 3 PM. An invite anchored to New York keeps 10 AM there, while London’s displayed time changes; using a calendar does not preserve both local times.
See the guide on how Daylight Saving Time affects remote teams for a full breakdown of these transition windows.
Frequently Asked Questions
- What is the difference between EST and EDT?
- EST always means UTC−5, while EDT means UTC−4. New York uses EST between its November and March clock changes and EDT between March and November. Some places, such as Jamaica, use EST year-round.
- Is it EST or EDT right now?
- From the second Sunday of March through the first Sunday of November, New York and other eastern US states are on EDT (UTC−4), not EST. From November through March, they are on EST (UTC−5). Many people say 'EST' year-round, but the technically correct summer abbreviation is EDT.
- What is the difference between PST and PDT?
- PST (Pacific Standard Time) is UTC−8 and applies from the first Sunday of November through the second Sunday of March. PDT (Pacific Daylight Time) is UTC−7 and applies in summer. Los Angeles, San Francisco and Seattle switch between PST and PDT on the same dates as the eastern US switches between EST and EDT.
- Why do some converters show the wrong time for EST?
- EST = UTC−5 is correct year-round as a fixed-abbreviation definition. A different answer is needed if someone actually means New York local time during EDT (UTC−4). Confirm the intended city and date rather than silently changing EST to EDT.
- Does the EST to PST offset change with DST?
- No — EST and PST are both standard-time labels, so the gap between them is always 3 hours (UTC−5 minus UTC−8). Likewise, the gap between EDT and PDT is always 3 hours (UTC−4 minus UTC−7). New York and Los Angeles change on the same dates, so their usual city-time gap also stays three hours across seasons. Because each changes at 2 AM local time, brief exceptions occur during the changeover hours, not for several weeks.
- What is the EST to PDT or EDT to PST situation?
- As literal offsets, EST (UTC−5) is two hours ahead of PDT (UTC−7), while EDT (UTC−4) is four hours ahead of PST (UTC−8). For New York and Los Angeles, use city names and the actual date; do not assume mixed standard/daylight labels describe both cities at that instant.