What is the CST to IST Converter?
This tool converts a time in the US Central Time Zone to India Standard Time (IST). India does not observe daylight saving time, but the US Central Zone switches between Central Standard Time (CST, UTC−6) in winter and Central Daylight Time (CDT, UTC−5) in summer. IST is fixed at UTC+5:30, so the gap is 11 hours 30 minutes from CST and 10 hours 30 minutes from CDT.
How to Use It
Enter the Central Time hour (0–23) and minute, then choose whether the date falls under standard time (CST) or daylight saving (CDT). The converter adds the correct offset and tells you the IST time and whether the result rolls into the next day.
The Formula Explained
The offset in minutes is 690 for CST (\(11\times60+30\)) or 630 for CDT (\(10\times60+30\)). We compute total minutes = hour×60 + minute + offset, then take the result modulo 1440 (minutes in a day) for the IST clock time and divide by 1440 to find the day shift.
$$\text{IST} = \left(\text{Hour (CST)} \times 60 + \text{Minute} + 690\right) \bmod 1440$$
Worked Example
At 9:00 CST:
$$9\times60 + 0 + 690 = 1230 \text{ minutes} = 20{:}30 \text{ IST, same day.}$$At 21:00 CST:
$$21\times60 + 690 = 1950 \text{ minutes}; \quad 1950 - 1440 = 510 = 08{:}30 \text{ IST, next day } (+1).$$FAQ
How far ahead is IST of CST? 11 hours and 30 minutes during standard time.
What about daylight saving? During CDT (summer) the difference shrinks to 10 hours 30 minutes because Central moves to UTC−5.
Does India use daylight saving? No, India stays on UTC+5:30 all year.
