How the maximum age at entry is calculated in any life insurance contract?

[vinit]

For example as per insurance plan, the maximum age at entry = 55.
Date of Birth (DOB) of the proposer is 01/04/1958.

1- So how this age of 55 is calculated?
2- Till when I am eligible to buy the above insurance plan?

[Rahul]

Please first read the offer document.

But as a standard, the calculation happens this way - 55 years minus 1 day or 54 years 364 days. So as per above example, you are eligible till 31/03/2013.