IST
Disambiguation — India (UTC+5:30), Israel (UTC+2), or Irish Standard Time (UTC+1).
Multiple time zones share this abbreviation
IST can refer to different time zones depending on the region. Choose the one you mean:
Where this abbreviation is used
| Meaning | Offset | Region |
|---|---|---|
| India Standard Time | UTC+5:30 | India |
| Israel Standard Time | UTC+2 | Israel |
| Irish Standard Time | UTC+1 | Ireland |
Countries using this zone
- India
- Israel
- Ireland
Principal cities
- New Delhi
- Mumbai
- Jerusalem
- Tel Aviv
- Dublin
- Kolkata
- Bengaluru
- Cork
History
India adopted a single unified standard time on 1 January 1906 to synchronize its vast rail and telegraph networks. Israel refined its daylight saving schedule through the Time Law of 1992, which was later updated in July 2013 to extend the summer period until late October. Ireland established the current definition of Irish Standard Time through the Standard Time Act 1968, designating the summer offset of UTC+1 as the official standard for the state.
Frequently Asked Questions
IST stands for India Standard Time (UTC+5:30), Israel Standard Time (UTC+2), and Irish Standard Time (UTC+1). These three distinct zones cover India, Israel, and Ireland respectively. Because the abbreviation is used in different parts of the world with varying offsets, users must specify the region to ensure accurate time coordination across international borders.
India does not currently observe Daylight Saving Time and remains on India Standard Time at UTC+5:30 consistently all year. This practice was established to avoid logistical confusion in a vast country with a high population density. Historically, India briefly utilized daylight shifts during certain global conflicts, but recent policy remains strictly fixed.
Israel Standard Time (IST) is the standard offset of UTC+2 used during winter months, while Israel Daylight Time (IDT) is the summer offset of UTC+3. The transition to IDT typically occurs on the Friday before the last Sunday of March, and the return to IST happens on the last Sunday of October at 2 AM local time.
Under the Standard Time Act 1968, Irish Standard Time is legally defined as UTC+1, which is observed during the summer. During the winter months, the country transitions to Greenwich Mean Time (GMT) at UTC+0. This arrangement is unique because the summer offset is officially designated as the standard time for the state.
Latest available data shows that approximately 1.45 billion people live within the India Standard Time zone, making it one of the most populated single time zones globally. In comparison, the populations using the Israel and Ireland variants are approximately 9.8 million and 5.3 million residents respectively, representing a significantly smaller share of global users.
Israel Standard Time (IST) changes to Israel Daylight Time (IDT) every year on the Friday before the last Sunday of March. At 2 AM local time, clocks move forward to 3 AM. This shift remains in effect until the last Sunday of October, when the region reverts to the UTC+2 standard offset.