CLST — Chile Summer Time (UTC−3)
CLST is Chile Summer Time, UTC−03:00. Chile from September to April — its summer, which is the northern winter. From spring to autumn the same clocks read CLT at UTC−04:00, so a CLST timestamp dated in winter is usually a mistake rather than a real offset. Put a timestamp into the panel below to read it in your own time.
A time written 15:00 CLST on is, in your time:
2026-07-27T15:00:00-03:00 Shown in UTC until your clock is read. Send the line above instead of the letters — it cannot be read two ways.
Where CLST is used
- UTC−03:00 Chile Summer Time Chile from September to April — its summer, which is the northern winter. America/Santiago
Reading a CLST timestamp
CLST is a fixed offset: UTC−03:00, always. That is worth stating plainly, because it is the part people get wrong. The abbreviation does not follow the clocks when they change — it names one side of the change. When Chile from September to April — its summer, which is the northern winter moves to summer time, the correct abbreviation becomes CLT at UTC−04:00; CLST does not quietly become an hour later.
So converting is arithmetic and nothing more. Add 3 hours to get UTC, then apply your own offset. The panel above does both steps and shows the result on your own clock, including the case that catches people out: a conversion that crosses midnight and lands on a different date from the one that was written down.
Write this instead
If you are the one sending the time, the fix is small and permanent. Use the IANA zone name — America/Santiago — or an ISO 8601 timestamp with a numeric offset, which looks like 2026-03-14T15:00:00-03:00. Both are unambiguous, both survive a daylight-saving change, and both are what calendar software and databases actually store underneath whatever they show you.
The zone name is the stronger of the two, because it carries the rules and not just the number. An offset is true for one instant; a zone is true for the year. If you write UTC−03:00 into a recurring meeting, half of that series will be an hour out after the clocks change, which is exactly what happens to a series pinned to CLST once CLT starts.
How to use this
- Type the date and time exactly as it was written to you, then read the row for the meaning you believe was intended.
- Switch to "I mean my own time" to go the other way: enter a time on your clock and see what it should be called.
- Copy the line at the bottom into your reply — an ISO timestamp with a numeric offset cannot be misread.
Worth knowing: Abbreviations are conventions, not standards. Some software emits CLST for zones that have no business using it, so treat the letters as a hint and the numeric offset as the fact.
FAQ
What does CLST stand for?
Chile Summer Time. It is UTC−03:00, which means a clock showing CLST is 3 hours behind UTC.
What is CLST in UTC?
UTC−03:00. To convert, add 3 hours to the CLST time to get UTC.
Should I write CLST in a calendar invite?
No. Write the IANA zone name instead — America/Santiago — or an ISO 8601 timestamp with a numeric offset. Calendar software resolves zone names correctly across daylight-saving changes, and a numeric offset cannot be read two ways. Three letters can.
What is the difference between CLST and CLT?
CLT is Chile Standard Time, UTC−04:00 — the winter half of the same year in the same places. CLST is the summer form, UTC−03:00. They are one hour apart and both are correct, on the right dates.