Function builtin_difftime 

fn builtin_difftime(
    args: &[RValue],
    named: &[(String, RValue)],
) -> Result<RValue, RError>

Compute the time difference between two date-time values.

@param time1 first POSIXct or Date value @param time2 second POSIXct or Date value @param units time unit for the result: “secs”, “mins”, “hours”, “days”, or “weeks” @return a difftime object (numeric with class and units attributes)