Time zone · Oceania
CIST
Cook Islands Standard Time
CIST is a single‑zone region at a steady UTC‑10:00. Rarotonga sits in a calm, year‑round offset with no daylight saving, making it easy to coordinate with a small‑step offset toward the Asia side of the Pacific.
Friday, June 5, 2026
Current offset
UTC-10:00
Standard · -10
Daylight saving
Not observed
Year-round standard time
IANA zones
1
None observe daylight saving
DST offset
—
No summer variant
About CIST
A fixed, year-round offset.
CIST is a single‑zone region at a steady UTC‑10:00. Rarotonga sits in a calm, year‑round offset with no daylight saving, making it easy to coordinate with a small‑step offset toward the Asia side of the Pacific.
IANA zones · the technical identifiers
The zone that resolve to CIST.
For software, always store the IANA identifier — never the abbreviation alone. The database keeps these zones distinct because their rules can, and historically did, diverge.
Cities currently on CIST
The same hour, city by city.
1 city · all UTC-10:00
Where CIST is used
One country.
Same offset · UTC-10:00
Other zones at UTC-10:00 right now.
These named zones share CIST's offset today. When daylight saving rules differ, they drift apart for part of the year.
Frequently asked questions
Common questions about CIST, daylight saving, and how to handle it in software. Can't find what you need? Email [email protected].
- How unusual is a region with just one official zone?
- Very. Most codes cover multiple members; CIST is essentially a solo zone, simplifying all comparisons and scheduling for Rarotonga.
- Roughly halfway between which global regions is this zone?
- Roughly central in the Pacific, sitting well east of Samoa Time but far west of Hawaii, creating common shorthand like 'halfway across the Pacific'.
- CIST offset simplified in last century?
- simplified in 1991, and remained steady since, minor adjustments after minor historical adjustments
- Why might this zone have removed DST?
- Very small landmass and tourism industry are small enough that clocks remain constant.
- Small team remote work advice?
- With a steady 10 hours behind UTC and reliable systems or Asia (+ small time difference)
- No DST, so you might ask why?
- Simplicity and avoided date line issues.
- Global counterpart time?
- Often used as a reference for 'halfway across the Pacific'
- Future changes expected?
- It is stable now.
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