IST stands for Indian Standard Time. It is the official time used throughout India and is set at UTC+5:30. Unlike many countries, India does not change clocks for daylight saving time, so the offset remains the same in January, June, October and every other month.
Software systems usually represent India time using the IANA timezone name Asia/Kolkata. This is the correct timezone identifier for Delhi, Mumbai, Bengaluru, Chennai, Hyderabad, Ahmedabad, Pune, Kolkata and all other Indian cities, even though the official standard meridian is associated with 82.5 degrees east near Mirzapur.