The offset never changes. India sits at UTC+5:30, Japan at UTC+9. That gap is a permanent 3 hours and 30 minutes. Add 3:30 to any IST time to land on JST. Subtract 3:30 to go the other way. No daylight saving adjustments, no seasonal surprises.
IST to JST at a glance
IST (India)
JST (Japan)
00:00
03:30
06:00
09:30
09:00
12:30
12:00
15:30
15:00
18:30
18:00
21:30
21:00
00:30 (next day)
When do working hours overlap between India and Japan?
Real-time collaboration works best from 11:00 to 16:00 IST. That maps to 14:30-19:30 JST.
It catches the late Indian morning through early afternoon and the Japanese afternoon into early evening. Outside that band, one side is asleep or off the clock.
Need a time outside the overlap? Check exact moments with the IST Converter.
Frequently asked questions about IST and JST time
Is Japan ever 4.5 hours ahead of India?
No. Japan does not observe daylight saving time, and neither does India. The difference is always 3 hours 30 minutes, year-round.
What is the time in Tokyo when it is 9 AM in Mumbai?
09:00 IST is 12:30 JST. Tokyo is 3.5 hours ahead of Mumbai.
Do I need to account for DST when converting IST to JST?
No. Both zones are fixed offsets. You never need to adjust for daylight saving time.
What is the best time to call from India to Japan?
11:00-16:00 IST, which corresponds to 14:30-19:30 JST. This overlaps the standard working hours in both countries.
Does Japan have multiple time zones?
No. Japan uses a single time zone, JST (UTC+9), for the entire country. The IANA zone is Asia/Tokyo.
Where can I convert other time zones from IST?
Use the IST Converter to convert India Standard Time to any zone worldwide. For more on IST itself, see What Is IST?.
How many hours ahead is JST of IST?
JST (UTC+9) is 3.5 hours ahead of IST (UTC+5:30).
Does the time difference between IST and JST change during the year?
No, it stays 3.5 hours ahead all year because neither place changes its clocks.