What is the validity period of e-way bill? When its countdown starts?

The validity period of E-way bill is prescribed in the Central Goods and Services Tax Act, 2017 as given below: In case of over dimensional cargo: Upto 20 kms within the Country - One day Thereafter, for every additional 20 kms or part thereof - One additional day In case of other than over dimensional cargo: Upto 100 kms within the Country - One day Thereafter, for every additional 100 kms or part thereof - One additional day In terms of Explanation 1 to Rule 138 CGST Rules, 2017, the validity an E-way bill starts from the time at which the E-way bill has been generated and each day shall be counted as the period expiring at midnight of the day immediately following the date of generation of e-way bill.