CST to IST Converter
CST to IST Converter works out Converted date and time and Converted date from Date and Time. The default figures on this page give converted date and time of 2025-01-15 23:30 (Wednesday, UTC+05:30); change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Source wall time: 2025-01-15 12:00 in America/Chicago, offset UTC-06:00.
- Convert to the absolute instant: 2025-01-15 18:00 UTC.
- Read that instant in Asia/Kolkata, whose offset on that date is UTC+05:30: 2025-01-15 23:30.
- Difference = 5.5 h - (-6 h) = 11.5 h.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the CST to IST Converter calculates
Converts a date and time between time zones using the IANA rules in force on that date, plans a meeting across several zones at once, and re-times a fixed dosing schedule after travel.
How to use this CST to IST Converter
Enter Date and Time. Converted date and time updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Converted date and time, Converted date and Converted time.
The method follows IANA Time Zone Database (tzdb), TC39 Temporal proposal - ZonedDateTime disambiguation, ECMA-402 Internationalization API, Intl.DateTimeFormat and NIST, Time Zones and Daylight Saving Time.
What you can compare
Change one input at a time to see how it affects Converted date and time, Converted date and Converted time. The inputs you can vary are Date and Time.
Understanding Converted date and time, Converted date and Converted time
Daylight-saving rules change. Confirm the offset against a current tz database release before relying on a conversion far in the future, and confirm any medication schedule with the prescriber.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
What information do I need for the CST to IST Converter?
You need Date and Time. The page opens with default figures that give converted date and time of 2025-01-15 23:30 (Wednesday, UTC+05:30), so you can see the scale before entering your own.
What does this CST to IST Converter show?
It shows Converted date and time, Converted date, Converted time, Converted date falls on, From zone, To zone, From zone UTC offset and To zone UTC offset, with the working and any warnings for your entries.
Can I check how the CST to IST Converter result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.