No. (It is Capital gain tax and is calculated on the basis of years - you get the benefit of "Cost Inflation Index" abbreviated as CII )
You can see the chart from 1981 to today from the following links ( Official PDF for capital gain is available at Income Tax site).
Suppose you don't have the actual Cost of Acquisition of the land then you can calculate on the basis of fair market value as on 1st April 1981 (Get the property valuation done by a Approved Registered Valuer as on 1st April 1981 and use it as COA).
So COA (Cost of Acquisition) = Fair Market Value as on 1st April 1981 + any other cost incurred thereafter for development etc.
Thereafter you can calculate by the formula :
Capital Gain = Sale Price - Indexed Cost of the Property (Further any expense occurred while selling can also be deducted such as brokerage & other expenses)
Indexed Cost of the Property = Actual COA x (Index in the year of Sale which is 2017 / Index in the Year of Purchase which is 1981 in your case)
So suppose the COA was ₹4 Lakh (as on 1-04-1981) & you sold the property for ₹50 Lakh ( Since the CII value is not yet announced for 2017-2018 we will consider that the property was sold in 2016-2017 i.e. Last year for our calculations)
Now the Indexed Cost of the Property = COA x (CII of 2016-17 / CII of 1981-82) = ₹4 Lakh x (1125 / 100) = ₹45 Lakh
So the Capital Gain = Sale Price - Indexed Cost of the Property = ₹50 Lakh - ₹45 Lakh = ₹5 Lakh
If the Seller of the property are more than one person then this gain would divide among them according to the share in the property.
So it has nothing to do with the Government value. The Government value is the minimum value fixed for the collection of Stamp Duty etc.
If you sell your property this year then you should use the CII of 2017-2018.
Hope this helps.