Calculate business hours between two dates

Question

How can I calculate business hours between two dates? For example we have two dates; 01/01/2010 15:00 and 04/01/2010 12:00 And we have working hours 09:00 to 17:00 in weekda

Answer 1

Another way of thinking, the below function work correctly if your first day of week is Monday otherwise you should change related lines including (6,7) to your local weekend's days

create function fn_worktime(@Datetime1 DateTime,@Datetime2 DateTime)
Returns BigInt
as
Begin
    Declare 
            @Date1 Date, 
            @Date2 Date,
            @DateIndex Date,
            @minutes int,
            @lastDayMinutes int,
            @StartTime int , --in minutes
            @FinishTime int ,--in minutes
            @WorkDayLong int --in minutes

    Set @StartTime  =8 * 60 + 30 -- 8:30
    Set @FinishTime =17* 60 + 30 -- 17:30
    Set @WorkDayLong =@FinishTime - @StartTime  

    Set @Date1 = Convert(Date,@DateTime1)
    Set @Date2 = Convert(Date,@DateTime2)
    Set @minutes=DateDiff(minute,@DateTime1,DateAdd(MINUTE,@FinishTime ,convert(DateTime,@Date1)))
    if @minutes<0 OR DatePart(dw,@Date1) in (6,7)  -- you can even check holdays here. '(6 Saturday,7 Sunday) according to SET DATEFIRST 1'
        Set @minutes=0

    Set @DateIndex=DateAdd(day,1,@Date1)
    While @DateIndex<@Date2
    Begin
        if DatePart(dw,@DateIndex) not in (6,7)  -- you can even check holdays here. '(6 Saturday,7 Sunday) according to SET DATEFIRST 1'
            set @minutes=@minutes+@WorkDayLong 
        Set @DateIndex=DateAdd(day,1,@DateIndex)
    End
    if DatePart(dw,@DateIndex) not in (6,7)  -- you can even check holdays here
    Begin
        set @lastDayMinutes=DateDiff(minute,DateAdd(MINUTE ,@StartTime ,convert(DateTime,@Date2)),@DateTime2)
        if @lastDayMinutes>@WorkDayLong 
            set @lastDayMinutes=@WorkDayLong 
        if @Date1<>@Date2   
            set @minutes=@minutes+@lastDayMinutes
        Else
            Set @minutes=@minutes+@lastDayMinutes-@WorkDayLong 

    End
    return @minutes
End