“You need to undergo the medical tests within 6 months from the departure date”

Question

I want to make a statement that means you need to undergo the medical tests not before 6 months from the date of departure.

In other words, the medical tests should not be taken earlier than 6 months or trying again "within 6 months period prior to the departure date".

I am confused as to which one is correct:

1. You need to undergo the medical tests within 6 months from the departure date.
2. You need to undergo the medical tests not before 6 months from the departure date.
3. You need to undergo the medical tests within 6 months period prior to the departure date.

Please help with the correct wording. Emphasis used only to illustrate the troublesome part.

Answer 1

The closest choice would be:

1. You need to undergo the medical tests within 6 months period prior to the departure date.

However, to be clear and easy to understand, you would better rewrite it as:

You need to undergo the medical tests within the period of six months prior to the departure date.

(Numbers less than thirteen are usually spelt out).

Answer 2

I have two suggestions, of which I like the first better.

You need to get the medical tests during the six months before your departure date.

You need to get the medical tests no earlier than six months before your departure date.

The preposition within is usually used for time periods after the reference time, so within six months of the departure date would normally be understood to mean the six months after the departure date. Using it for the earlier time period is confusing.

Answer 3

You could always just spell it out and be super-clear:

You need to undergo the medical tests prior to the departure date, but no more than six months before.

Answer 4

I would suggest a rewrite like this:

A medical test must be taken inside the six month time window before your departure date.

Answer 5

"you need to do this within 6 months of the departure date" can also mean within the 6 months before the departure. If you fear there will be some confusion whether you mean before or after the departure, say "within the 6 months prior to departure"