All year, the same gap
Neither India nor Tokyo changes its clocks, so the gap is the same on every date. IST here means India Standard Time.
12:00 PM Wednesday 15 Jul in India is 3:30 PM Wednesday 15 Jul in Tokyo (JST, 3 h 30 min ahead).
Why daylight saving conversions need a date explains skipped and repeated clock readings. The rules here come from the browser’s time zone data and can lag a government change.