experimental chemistry - Why a specific temperature for value of 1 calorie?

Everything in chemistry often comes with a strong reason and facts behind it, but I stuck in definition of $1$ calorie.

My reference book define one calorie as amount of heat required to raise the temperature of one gram of water from $14.5$ degrees Celsius to $15.5$ degrees Celsius.

Why $14.5$ and $15.5$, why temperature such as $0$ to $1$ or $19$ to $20$ degree Celsius is not chosen?

Please forgive me if this question is too easy and I can't figure out the logic related to it.

I shall be glad to have your suggestions.

Answer

why temperature such as 0 or 1 degree celsius is not chosen??

That has been chosen by some.

According to Physical Laboratory Experiments: Part III.--Heat, 4th edition (1912) :

The following different calories should not be confused:

1. 
   

   ZERO DEGREE CALORIE:- The quantity of heat required to raise one gram of water from 0 [degrees] C to 1 [degree] C.

   
   


2. 
   

   ORDINARY CALORIE: cal.-The quantity of heat required to raise one gram of water from 15 [degrees] C to 16 [degree] C, this being taken as the mean room temperature.

   
   


3. 
   
   

   MEAN CALORIE OR ICE CALORIMETER CALORIE: The one-hundred part of heat required to raise one gram of water from 0 [degrees] C to 100 [degrees] C.

   
   


4. 
   

   ...

   
   

Heat capacity of liquid water is a continuously varying function of temperature itself, so a particular temperature or temperature interval must be specified. Various intervals were chosen historically, and when a small interval near 15 degrees C is chosen it is because that was thought of as room temperature 100-200 years ago.