There are no built-in functions for determining and converting timezones. To fix this problem, we can enhance the capabilities of the Excel Time() function.
=A1+Time(5,30,0)
You'll need to add 5 hours and 30 minutes for IST. Similarly, by adding or removing the time difference, you can convert to any timezone.
Hours, minutes, and seconds are the three inputs to Time().
This function returns a serial number formatted timestamp. This number will be interpreted by Excel, and the timestamp will be displayed in a legible format.