Retirement on attaining the age of 58 - technically isn't on date ascertained

My date of birth is 18th September 1960. I have been informed by my organisation that I will retire on 17th September 2018 which is on attaining the age of 58 years. My query ..... technically isn't 17th September 2018 still in my 57th year?
Also does attaining the age of 58 start from 18th September 2018 or will it be 17th September 2019. Need legal help on this please.

Produce a original valid school leaving certificate / aadhar card, as a proof of your date of birth and request the management to consider.

When do you attain the age of 58?
DOB 18 Sep 1960
As per calculations you will attain 58 on 18 Sep 2018 and so have to retire as per your organisational laws/rules.

Age is computed on the basis of completed year only. Right from your date of birth, you would be completing 58 years of age just a day before your actual date of birth i.e 17-09-2018. From 18-09-2018 you would be stepping into your 59th year of age. Therefore, your management's contention is correct. Even in the case of Govt employees who are permitted to retire on the last working day of their birth month irrespective of the actual day of birth in the month, a person born on the first day of a month would be retired on the last day of the previous month only.

Dear Friends
There should not be any type of misunderstanding ,age of retirement is fixed I,e.58 yers.58Years can be completed on any date of the month.It is a universal practice -if the employee's date of birth is with in 15 then mgt can relieve on previous month's last day otherwise it will be last day of the current month.
Like this queries were discussed earlier also.

As per your date of birth, your retirement date would be 17th September 2018. There is nothing wrong since on 17/09/18 you are completing age of 58 years and thereafter your age always would be 58 plus. The date has been informed to you by your organisation is correct and 17/08/2018 will be your last working day.
You can take legal help but would reap nothing rather than unnecessary expenditure and mental agony.

However Retirement age is decided on completion of stipulated age, in your case if company has fix the age of retirement i.e. 58 years than retirement effective on completion of 58 years, considering your birth date 18-09-1960, then 58 years will be completed on night 17-09-2018 00.00 hours when starting of next date i.e. 18-09-2018.
Hence if you go deeply in terms you will completed 58 years on 00.00 hours on 17-09-2018 night (or you can say starting of morning of next day).