# Returns a new Date/DateTime representing the "start" of this week, week starts on start_day (i.e, Monday; DateTime objects will have time set to 0:00).
# Returns a new Date/DateTime representing the "start" of this week, week starts on start_day (default is :monday, i.e. Monday; DateTime objects will have time set to 0:00).
# Returns a new Date/DateTime representing the end of this week, week starts on start_day (Sunday, DateTime objects will have time set to 23:59:59).
# Returns a new Date/DateTime representing the end of this week, week starts on start_day (default is :monday, i.e. Sunday, DateTime objects will have time set to 23:59:59).