diff_days: Number of days between two gregorian dates
In edgararuiz/maya: Converts between Mayan and Gregorian calendars

It determines the number of days between two gregorian dates. It works independently from any R date/time function. An advantage of this function is that it is accepts dates older than year 1 CE. It uses calendar and not astronomical year numbering.

1	diff_days(from_date, to_date)

`year_1`	A positive integer
`month_1`	A positive integer
`day_1`	A positive integer
`bce_1`	Logical variable, indicates if the date is Before Common Era
`year_2`	A positive integer
`month_2`	A positive integer
`day_2`	A positive integer
`bce_2`	Logical variable, indicates if the date is Before Common Era