Question

what is Indian Standard Meridian

Answer 1

Indian Standard Meridian passes through Allahabad at 82.5 degree of east.

It has taken as ISM because it passes middle of the country

I hope it helps you
tq

^_^

Answer 2

british india did not adopt the international standard time zone until 1905 when the , meridian passing through allahabad (82.5 east) of ( greenwich meridian longitude) was picked as central meridian of india corresponding to a simple time zone for country at 5hrs 30 minutes in advance of gmt