The Day Counters on EasySurf count days exclusively.
The "From" date is subtracted from the "To" date.
This is the way spreadsheet programs count days.
If you are counting time in a continuous (uninterrupted in time) way then you are counting days exclusively.
Exclusive counting is used to determine how much time has elapsed between to dates.
If the days you want to count are discrete days then you want to count the days inclusively.
For example, if you want to count sick days or vacation days then you want to count the days inclusively.
To use the EasySurf Day Counter to count these days then you must add one day to the results.

Between
There are two definitions for the word "between" that must be considered when counting days.

Between: from one to another for example "air service between Miami and Chicago"
This is the way "between" is used on EasySurf.

Between: the interval that separates two things
If we have a row of letters "ABCDE", and we ask how many letters are between
"A" and "E" the answer is B, C and D or three letters. If you want to use this definition of
"between" then you must subtract one day from the results.

Weeks
The number of weeks is calculated by dividing the number of days by seven.