Difference Between CST and IST


CST is Central Standard Time observed in the US while IST stands for Indian Standard Time that is observed across whole of India. Difference between CST and IST can be easily calculated with reference to GMT. While IST is 5:30 hours ahead of GMT, CST is 6 hours behind GMT. This means that IST is in effect +11:30 of CST. In other words, CST lags behind IST by 11:30 hours. So if it is 12 noon on any given date in the US according to CST, it will be close to midnight on the same day in India as according to IST, it will be 1:30 P.M in India at the same instant. Let us see how this difference is generated.

It is Allahabad in India which is taken as reference to set the time across the country. The location of Allahabad is 82.5 degree east of the Prime Meridian. For every 15 degree there is a difference of 1 hour from GMT. Since in this case it is 82.5 degrees, the time difference with GMT comes to exactly 5 hours and 30 minutes. IST came into effect in 1955 before which there were two standard times observed in India (Bombay time and Calcutta time).

On the other hand, CST is 90 degree west of Greenwich Mean Time which makes it ahead of the GMT by 6 hours. So when it is 12 noon at GMT, the time according to CST is 6 P.M.

In brief:


• CST is the time observed in America, whereas IST is the Indian Standard Time observed in India.

• CST is 6 hours behind GMT, while IST is 5:30 hours ahead of GMT. This makes IST ahead of CST by exactly 11:30 hours.