IST to AST Converter
Understanding IST and AST Time Zones
India Standard Time (IST)
India Standard Time is observed in undefined and uses the offset UTC+5.5. Major cities in this time zone include Mumbai, Delhi, Bangalore. This time zone serves a significant global region with important economic and cultural hubs.
Atlantic Standard Time (AST)
Atlantic Standard Time operates at UTC-4, covering undefined. Key cities include Halifax, San Juan. The 9.5-hour backward offset from IST means that when professionals in Mumbai start their workday at 9:00 AM, it is already 11:30 PM in Halifax.
IST is also commonly referred to as India time, Indian time, Mumbai time, Delhi time. AST is also known as Atlantic Time, Puerto Rico time. So if you are searching for India time to Atlantic Time, this is the same conversion as IST to AST.
Complete IST to AST Conversion Table
The table below shows every two-hour increment converted from India Standard Time to Atlantic Standard Time. Business hours (9 AM – 5 PM) are highlighted for easy scheduling reference.
| IST (India Standard Time) | AST (Atlantic Standard Time) |
|---|---|
| 12:00 AM (00:00) | 2:30 PM (14:30) (previous day) |
| 2:00 AM (02:00) | 4:30 PM (16:30) (previous day) |
| 4:00 AM (04:00) | 6:30 PM (18:30) (previous day) |
| 6:00 AM (06:00) | 8:30 PM (20:30) (previous day) |
| 8:00 AM (08:00) | 10:30 PM (22:30) (previous day) |
| 10:00 AM (10:00) | 12:30 AM (00:30) |
| 12:00 PM (12:00) | 2:30 AM (02:30) |
| 2:00 PM (14:00) | 4:30 AM (04:30) |
| 4:00 PM (16:00) | 6:30 AM (06:30) |
| 6:00 PM (18:00) | 8:30 AM (08:30) |
| 8:00 PM (20:00) | 10:30 AM (10:30) |
| 10:00 PM (22:00) | 12:30 PM (12:30) |
Times shown in 12-hour and 24-hour format. Last updated 2026-03-09.
Scheduling Between IST and AST
Remote teams spanning Mumbai and Halifax often adopt asynchronous practices to bridge the 9.5-hour gap. Tools like Slack, Loom, and Notion reduce the need for real-time overlap while keeping projects moving forward.
The large 9.5-hour gap between IST and AST means that finding overlapping working hours requires compromise from at least one side. Consider adopting asynchronous workflows — recorded video updates, shared documents, and time-zone-aware project management tools — to supplement the limited real-time overlap.
Travel Between Mumbai and Halifax
When arriving in Halifax from Mumbai, immediately set all devices to local time. Exposure to natural daylight at the destination helps reset your circadian rhythm. Westbound travelers should seek afternoon light.
Medical experts recommend allowing approximately one day of adjustment per hour of time difference. For the 9.5-hour shift between IST and AST, plan for roughly one week of gradual adjustment for optimal performance.
Daylight Saving Time Considerations
Keep in mind that DST transition dates differ between regions. The US changes clocks in March and November, Europe in March and October, and Australia in April and October. This can cause temporary shifts in conversion results.
For the IST to AST conversion specifically: IST (UTC+5.5) and AST (UTC-4) neither observes DST, so the 9.5-hour offset remains constant throughout the year. This makes scheduling reliable and predictable.
Related Time Zone Conversions
References & Resources
Frequently Asked Questions
IST (India Standard Time) is 9.5 hours ahead of AST (Atlantic Standard Time). IST is UTC+5.5 and AST is UTC-4.
When it is 12:00 PM (noon) in IST, it is 2:30 AM in AST.
The best overlap for business hours is approximately 11:00 PM to 7:00 AM AST, which corresponds to 9:00 AM to 5:00 PM in IST. Given the large gap, consider alternating between early and late meeting times.
Keep in mind that DST transition dates differ between regions. The US changes clocks in March and November, Europe in March and October, and Australia in April and October. This can cause temporary shifts in conversion results.