nicholaskajoh

/* calculate the difference in minutes between 2 date times
  given that only the minutes within a specified time range
  every day should be counted
  e.g: say the time range is 6AM to 6PM
  if datetime1 = 4AM and datetime2 = 5AM, difference = 0 minutes
  this is because 4AM to 5AM doesn't fall within the range of
  6AM to 6PM so the 60 minutes isn't counted
  e.g 2: say we have same time range and,
  datetime1 = 5AM today and datetime2 = 7PM tomorrow,
  difference = 1440 minutes