You might want to actually study the word Jerry it was never used as a time period the word literally means a dispensing as in Paul being dispensed GRACE by Jesus, and every time the word "dispensation" is used in scripture it means a dispensing NEVER a time period.
Depends on how it is used
as a general principle, or rule of thumb.
A dispensation is a noun when it is referring to that which is dispensed; which is not a noun.
And then there is the verb "dispensing" or "delivering."
As in "I delivered unto you that which I also received" or which was also dispensed, or "delivered unto me..."
When that which is dispensed or delivered by the dispenser to the dispensee, it is a dispensation.
The following is a "carnal" example of that (as the Lord sometimes had the Apostle Paul put that, when using an example from every day life towards illustrating a principle, or principles).
Go down to your neighborhood store's paint department.
Ask to have mixed, say, a shot of sky blue in a gallon of white paint.
Someone will take that can of white paint, walk it over to the Paint Mix Dispenser, and press a series of buttons instructing it as to what quantity of blue mix to dispense into your gallon of white paint, as a dispensation of blue mix.
While you are waiting for that dispensation of blue mix to end, the little window on the Paint Mix Dispenser will read "dispensing."
The person who set all that in motion being you; the person who committed said dispensation unto said individual.
Should their boss show up to instruct them to go to lunch, they could say "after I am through with this order...for a dispensation of (from) this customer, has been committed unto me."
Lastly, as Stam also rightly pointed out, that said dispensation of blue mix, in this example, took a period of time for it's intended dispensing or dispensation to reach its intended fullness, does not mean that a dispensation is a period of time.
Only that it takes place over one.
Or as the Lord put it "It is not for you to know the times or the seasons which the Father has put in His own power" - in other words..."no man knoweth the day, nor the hour, but only the Father..."
The word "dispensation" encompasses all that
as a general principle or rule of thumb, in The Lord's use of all it's related aspects through the pen of the Apostle Paul; whether or not the word is translated as such.
Yours in Him,
Rom. 5:8
Prov. 27:17