Which zone this page means. IST means India Standard Time (UTC+5:30), Irish Standard Time (UTC+1) and Israel Standard Time (UTC+2). This page means the Indian zone, which is one of the few on a half-hour offset. CST means US Central Standard Time (UTC-6) and also China Standard Time (UTC+8) — fourteen hours apart. This page means the US zone. For the Chinese zone see China Standard Time.
IST is ahead of CST by 10.5 hours today
On 19 August 2026, India Standard Time is on IST at UTC+05:30 and Central Standard Time (US) is on CDT at UTC-05:00. The gap between them is 10.5 hours, with CST behind. So 9:00 am in IST is 10:00 pm in CST, and 5:00 pm in IST is 6:00 am in CST. Going the other way, see CST to IST.
The gap is not constant, and that is the part that catches people out
Central Standard Time (US) is currently observing daylight saving and changes next on 1 November 2026. India Standard Time does not observe daylight saving, so the gap moves only when Central Standard Time (US) changes its clocks — twice a year, by one hour.
When you can actually both be at work
Taking a working day as 9:00 am to 5:00 pm local at each end, there are 0 overlapping hours in a normal day. There is none: the two working days do not touch at all, so any live meeting between India Standard Time and Central Standard Time (US) has to sit outside somebody's normal hours. The table above shows which end has the shorter stretch to give up.
Zone rules are set by legislation and change, sometimes at short notice. This page is built against tzdata 2026a, last reviewed 2026-08-18. Quarterly. Zone rules change by legislation, sometimes at short notice. Version and review date are shown on every zone page. The converter above reads your browser's own copy of the zone database, so if a rule has changed since this page was built the live answer follows the new rule.
Every convention used above — whether the start date counts, how month ends are clamped, which holidays close an office — is written out on the methodology page, including the daylight-saving rules behind the 10.5-hour gap above.