IST to GMT Converter
Convert time between India Standard Time (IST) and Greenwich Mean Time (GMT)
India Standard Time (IST)
Greenwich Mean Time (GMT)
Time Difference
Greenwich Mean Time (GMT) is 0 hours ahead of India Standard Time (IST)
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Select Time
Quick Reference
| IST | GMT |
|---|---|
| 07:30 | 02:00 |
| 09:30 | 04:00 |
| 11:30 | 06:00 |
| 13:30 | 08:00 |
| 15:30 | 10:00 |
| 17:30 | 12:00 |
| 19:30 | 14:00 |
| 21:30 | 16:00 |
| 23:30 | 18:00 |
| 01:30 | 20:00 |
| 03:30 | 22:00 |
| 05:30 | 00:00 |
Top 10 Most Common Time Zones
| Abbreviation | Full Name | UTC Offset | Typical Use |
|---|---|---|---|
| UTC | Coordinated Universal Time | UTC ±0 | Global reference standard (servers, logs, APIs) |
| EST / EDT | Eastern (US) Time | UTC −5 / −4 | New York, Toronto — North American business hub |
| CST / CDT | Central (US) Time | UTC −6 / −5 | Chicago, Dallas — US central business region |
| PST / PDT | Pacific (US) Time | UTC −8 / −7 | San Francisco, Los Angeles — tech industry standard |
| GMT / BST | Greenwich Mean / British Summer Time | UTC 0 / +1 | UK, used globally as a reference with UTC |
| CET / CEST | Central European (Summer) Time | UTC +1 / +2 | Paris, Berlin, Amsterdam — EU business core |
| IST | India Standard Time | UTC +5:30 | India — major IT & outsourcing region |
| CST | China Standard Time | UTC +8 | Beijing, Shanghai — East Asia business hub |
| JST | Japan Standard Time | UTC +9 | Tokyo — finance & tech hub |
| AEST / AEDT | Australian Eastern (Daylight) Time | UTC +10 / +11 | Sydney, Melbourne — APAC regional business |
Why Time Zone Abbreviations Are Ambiguous
Unlike standardized identifiers (like America/New_York or Europe/London from the IANA tz database), abbreviations such as "CST" or "IST" are not globally unique. They can refer to different time zones depending on context — country, region, or even time of year (due to daylight saving time).
Common Ambiguous Time Zone Abbreviations
| Abbrev. | Common Meaning(s) | UTC Offset | Region(s) |
|---|---|---|---|
| CST | Central Standard Time / China Standard Time / Cuba Standard Time | UTC−6 / UTC+8 / UTC−5 | North America, China, Cuba |
| IST | Indian Standard Time / Irish Standard Time / Israel Standard Time | UTC+5:30 / UTC+1 / UTC+2 | India, Ireland, Israel |
| AST | Atlantic Standard Time / Arabia Standard Time | UTC−4 / UTC+3 | Caribbean, Canada, Middle East |
| PST | Pacific Standard Time / Philippine Standard Time | UTC−8 / UTC+8 | North America, Philippines |
| EST | Eastern Standard Time (North America / Australia) | UTC−5 / UTC+10 | North America, Australia |
✅ Best Practice
To avoid ambiguity, always:
- Use IANA tz identifiers — e.g.,
America/New_Yorkinstead of "EST" - Specify UTC offset explicitly — e.g.,
UTC−5when abbreviations must be used - Include the full timezone name — e.g., "Eastern Standard Time (EST)" with UTC offset
Related Time Zone Conversions
About IST to GMT Time Conversion
Converting time between India Standard Time (IST) and Greenwich Mean Time (GMT) is essential for coordinating between India and the United Kingdom and other GMT-based regions. IST is UTC+5:30 (consistent year-round, no daylight saving time), while GMT is UTC+0 (observed during winter, October to March). IST is 5.5 hours ahead of GMT.
This conversion is crucial for Indian companies coordinating with UK offices, financial institutions, and international organizations based in London. The time difference varies seasonally: 5.5 hours during GMT (winter, October-March) and 4.5 hours during BST (summer, March-October). India-UK business relationships span IT services, financial services, consulting, and business process outsourcing sectors. The GMT timezone is the standard reference for global time, making it essential for international coordination. Understanding both GMT and BST transitions is critical for managing recurring meetings and deadlines with UK-based partners.
Common Use Cases for IST to GMT Conversion
Business & Work
- Scheduling calls between Indian offices and London headquarters
- Coordinating software development teams across India and UK
- Managing financial operations and trade with UK-based institutions
- Planning international conferences and webinars with UK participants
Personal & Travel
- Coordinating with family and friends in the United Kingdom
- Planning travel between India and UK destinations
- Scheduling virtual meetings with UK-based relatives
- Arranging online collaboration with UK-based colleagues
Time Zone Information
India Standard Time (IST)
- UTC Offset: UTC+5:30
- IANA Timezone: Asia/Kolkata
- Daylight Saving: No daylight saving time (consistent year-round)
- Major Cities: New Delhi, Mumbai, Bangalore, Hyderabad, Chennai, Kolkata
- Coverage: Entire India (single timezone covering entire nation)
Greenwich Mean Time (GMT)
- UTC Offset: UTC+0 (UTC+1 during BST)
- IANA Timezone: Europe/London
- Daylight Saving: Winter time (last Sunday in October to last Sunday in March), Summer time BST (UTC+1)
- Major Cities: London, Manchester, Birmingham, Leeds, Glasgow, Edinburgh
- Coverage: United Kingdom, West Africa, Atlantic region (winter months)
Quick Reference: IST to GMT
Remember: IST is 5.5 hours ahead of GMT (October-March). When GMT transitions to BST (last Sunday in March), the difference becomes 4.5 hours. Always verify which period applies when scheduling.
Frequently Asked Questions
What is the time difference between IST and GMT?
India Standard Time (IST) is UTC+5:30, while Greenwich Mean Time (GMT) is UTC+0. This means IST is 5.5 hours ahead of GMT. When you have 12:00 PM in London (GMT), it's 5:30 PM the same day in India (IST).
How does GMT differ from BST, and how does it affect the time difference?
GMT (Greenwich Mean Time) is UTC+0 and is observed during winter (October-March). BST (British Summer Time) is UTC+1 and is observed during summer (March-October). IST is 5.5 hours ahead of GMT (winter) and 4.5 hours ahead of BST (summer). This means the difference changes seasonally by 1 hour.
Does India observe daylight saving time like GMT-based regions do?
No, India does not observe daylight saving time. India Standard Time remains UTC+5:30 throughout the year. This means IST is consistently 5.5 hours ahead of GMT during winter months and 4.5 hours ahead of BST during summer months.
When does GMT transition to BST, and how does this affect scheduling?
GMT transitions to BST on the last Sunday of March, and BST transitions back to GMT on the last Sunday of October. This 1-hour difference is significant for scheduling. From October to March, IST is 5.5 hours ahead of GMT. From March to October, IST is 4.5 hours ahead of BST.
What are the best times to schedule calls between India and UK/GMT regions?
During GMT (winter): Evening in India (6-8 PM IST) overlaps with early afternoon in UK (12:30-2:30 PM GMT). Morning in India (8-10 AM IST) overlaps with early morning UK (2:30-4:30 AM GMT). During BST (summer): Evening in India (6-8 PM IST) overlaps with afternoon UK (1:30-3:30 PM BST).
Why is GMT/BST important for India-UK business coordination?
GMT/BST is crucial because the UK is a major business hub with strong ties to India. The 4.5-5.5 hour time difference provides reasonable business hour overlap, making it suitable for real-time collaboration. India-UK coordination spans finance, IT services, business outsourcing, and consulting sectors with significant daily interactions.
Pro Tips
- • GMT and BST transitions happen on specific dates: last Sunday of March and October. Mark these in your calendar and adjust meeting times immediately after transitions.
- • The time difference varies by season: 5.5 hours during GMT (October-March) and 4.5 hours during BST (March-October). Always verify which period applies when scheduling recurring meetings.
- • Evening in India (6-8 PM IST) is the best overlap window with UK hours. This corresponds to early afternoon in GMT (12:30-2:30 PM) and afternoon in BST (1:30-3:30 PM).
- • Early morning in India (8-10 AM IST) provides minimal but possible overlap with early morning UK (2:30-4:30 AM GMT). Use this window only for time-sensitive matters.
- • The 5.5-hour offset (not a whole number) is unique to IST. When scheduling across time zones, account for this 30-minute difference in calculations.
- • Many India-UK businesses use asynchronous communication via email and recorded updates to manage the time difference. Reserve live meetings for critical discussions that require real-time interaction.
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