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Calculating an interval of time

Hi all,

i need to figure out how to calculate an interval of time - in ms.
I am working on a backup project that the user will run, select the date and time of the next run and then start the program.
This program will run on that day and time, then reset and run again the same day and time the next week.


For example, the user starts the program on Monday, at 11:24 am.
They select Friday, at 20:30 (8:30 pm) and start the program.  The code below calculates the number of ms for the interval of the System.Timers.Timer
Friday at 20:30 comes, the program runs and resets itself to run the next friday at 20:30 (recalculating the new interval)

what i'm needing to calculate is the interval from when the user clicks 'start' until the program actually runs.

What I have so far is
2 combo-boxes
(DayBox)  with Sunday-Saturday, so that the indecies of the combobox correspond with Date.DayOfWeek values, ie Sunday=0, Monday=1, etc)

(TimeBox) with times (in 24h format, in 30 minute increments - ie 00:00, 00:30, 01:00 ...... 23:00,23:30)

The following code seems to work, but after writing it, it seems very cumbersome.
Does anyone have a simpler, or more elegant way to do this?

Private Enum MSeconds
        Days = 86400000
        Hours = 3600000
        Minutes = 60000
        Seconds = 1000
End Enum
 
Private Function GetNextInterval() As Long
        Dim day As Integer = Now.DayOfWeek
        Dim day2 As Integer = DayBox.SelectedIndex
        Dim d As Integer = 0
        Dim h As Integer = CInt(Split(TimeBox.Text, ":")(0))
        Dim m As Integer = CInt(Split(TimeBox.Text, ":")(1))
        Dim s As Integer = 0
        ' number of days til next backup
        If day > day2 Then
            ' if today is past backup day
            d = 7 - (day - day2)
        ElseIf day2 > day Then
            d = day2 - day
        Else
            'day=day2
            Dim time As New Date(Now.Year, Now.Month, Now.Day, h, m, s)
            Dim ts As TimeSpan = time - Now
            If ts.TotalMilliseconds > 0 Then
                ' its passed already
                d = 6
            Else
                d = 0
            End If
        End If
 
        ' number of hours
        If h = 0 Then
            ' use 24
            If Now.Hour = 0 Then
                h = 0
            Else
                h = 24 - Now.Hour
            End If
        Else
            If h > Now.Hour Then
                h = h - Now.Hour
            ElseIf h < Now.Hour Then
                h = 24 - (Now.Hour - h)
            Else
                h = 0
            End If
        End If
        ' number of minutes
        If m = 0 Then
            ' use 60
            If m = Now.Minute Then
                m = 0
            Else
                m = 60 - m
            End If
        ElseIf m = 30 Then
            If m > Now.Minute Then
                m = 30 - Now.Minute
            Else
                m = 60 - (Now.Minute - m)
            End If
        End If
        ' number of secods - leave at 0
        s = 0
        Return d * MSeconds.Days + h * MSeconds.Hours + m * MSeconds.Minutes + s * MSeconds.Seconds
    End Function

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sgaggerj
Asked:
sgaggerj
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3 Solutions
 
Joel CoehoornDirector of Information TechnologyCommented:
Don't use a timer for this.  Set up a windows scheduled task instead.

But if you absolutely must use a timer, you're making this way too hard.  Just return the ts.TotalMilliseconds that you calculated at the top.
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orcicCommented:
I agree with jcoehoorn. Your simplified function would be something like....

Private Function GetNextInterval() As Long
        Dim day As Integer = Now.DayOfWeek
        Dim day2 As Integer = DayBox.SelectedIndex
        Dim d As Integer = 0
        Dim h As Integer = CInt(Split(TimeBox.Text, ":")(0))
        Dim m As Integer = CInt(Split(TimeBox.Text, ":")(1))
        Dim s As Integer = 0
        ' number of days til next backup
        If day > day2 Then
            ' if today is past backup day
            d = 7 - (day - day2)
        ElseIf day2 > day Then
            d = day2 - day
        Else
            'day=day2
            Dim time As New Date(Now.Year, Now.Month, Now.Day, h, m, s)
            Dim ts As TimeSpan = time - Now
            If ts.TotalMilliseconds > 0 Then
                ' its passed already
                d = 6
            Else
                d = 0
            End If
        End If
     Dim time1 As New Date(Now.Year, Now.Month, Now.Day+d, h, m, s)
     Dim ts1 As TimeSpan = time1 - Now
     Return ts1.TotalMilliseconds
  End Function
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orcicCommented:
replace
 Dim time1 As New Date(Now.Year, Now.Month, Now.Day+d, h, m, s)
with
  Dim time1 As Date
  time1=DateSerial (Now.Year, Now.Month, Now.Day+d).AddHours(h).AddMinutes(m).AddSeconds(s)
 
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sgaggerjAuthor Commented:
I think it should also be
Dim ts1 as TimeSpan
if (Now-time1).totalmilliseconds > 0 then
   ts1=now-time1
else
   ts1=time1-now
endif

otherwise it could return a negative value, right?

that's why i used
Dim l As Long = d * MSeconds.Days + h * MSeconds.Hours + m * MSeconds.Minutes + s * MSeconds.Seconds
so it would always be a positive value

however, i just ran a couple other tests and it doesn't seem to be working right.

If I have it start Monday, at 15:00 (now it's currently 13:20), it comes up with 6 days, 2 hours, etc etc.
it should only be 1 hour 40 minutes
because Monday at 3pm hasn't arrived yet.

i made a couple adjustments because the hours weren't working properly


Private Function GetNextInterval() As Long
        Dim day As Integer = Now.DayOfWeek
        Dim day2 As Integer = DayBox.SelectedIndex
        Dim d As Integer = 0
        Dim h As Integer = CInt(Split(TimeBox.Text, ":")(0))
        Dim m As Integer = CInt(Split(TimeBox.Text, ":")(1))
        Dim s As Integer = 0
        ' number of days til next backup
        If day > day2 Then
            ' if today is past backup day
            d = 7 - (day - day2)
        ElseIf day2 > day Then
            d = day2 - day
        Else
            'day=day2
            Dim time As New Date(Now.Year, Now.Month, Now.Day, h, m, s)
            If time > Now Then
                d = 0
            Else
                d = 6
            End If
            'Dim ts As TimeSpan = time - Now
            'If ts.TotalMilliseconds > 0 Then
            '    ' its passed already
            '    d = 6
            'Else
            '    d = 0
            'End If
        End If
 
        ' number of hours
        If h = 0 Then
            ' use 24
            If Now.Hour = 0 Then
                h = 0
            Else
                h = 24 - Now.Hour
            End If
        Else
            If h > Now.Hour Then
                h = h - Now.Hour
            ElseIf h < Now.Hour Then
                h = 24 - (Now.Hour - h)
            Else
                h = 0
            End If
        End If
        ' number of minutes
        If m = 0 Then
            ' use 60
            If m = Now.Minute Then
                m = 0
            Else
' CHANGED HERE FROM m=60-m and added h-=1
                m = 60 - Now.Minute
                h -= 1
            End If
        ElseIf m = 30 Then
            If m > Now.Minute Then
                m = 30 - Now.Minute
            Else
                m = 60 - (Now.Minute - m)
            End If
        End If
        ' number of secods - leave at 0
        s = 0
 
        Dim time1 As New Date
        time1 = DateSerial(Now.Year, Now.Month, Now.Day + d).AddHours(h).AddMinutes(m).AddSeconds(s)
        Dim ts1 As TimeSpan
        If (time1 - Now).TotalMilliseconds > 0 Then
            ts1 = time1 - Now
        Else
            ts1 = Now - time1
        End If
        EndTime = Now.AddMilliseconds(ts1.TotalMilliseconds)
        Return ts1.TotalMilliseconds
    End Function

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Mike TomlinsonMiddle School Assistant TeacherCommented:
Good grief...you waaaaaaaaaay overcomplicated it:
    Private Function GetNextInterval() As Long
        Dim h As Integer = CInt(Split(TimeBox.Text, ":")(0))
        Dim m As Integer = CInt(Split(TimeBox.Text, ":")(1))
        Dim dtBase As DateTime = DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek)
        Dim dtTarget As New DateTime(dtBase.Year, dtBase.Month, dtBase.Day, h, m, 0)
        If dtTarget < DateTime.Now Then
            dtTarget = dtTarget.AddDays(7)
        End If
        Return dtTarget.Subtract(DateTime.Now).TotalMilliseconds
    End Function

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Joel CoehoornDirector of Information TechnologyCommented:
One thing to remember:  Now is a very dynamic value, so this code is fatally flawed:
Dim ts1 as TimeSpan
if (Now-time1).totalmilliseconds > 0 then
   ts1=now-time1
else
   ts1=time1-now
endif

This would be more correct:
Dim ts1 as TimeSpan
Dim curTime As Date = Now
if (curTime - time1).totalmilliseconds > 0 then
   ts1=curTime - time1
else
   ts1=time1 - curTime 
endif

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sgaggerjAuthor Commented:
heheh 'good grief'.  Yea I know I have a wierd way of looking at things!

That's pretty much what i was looking for Idle...

i came up with something a little different

add

DayBox as DateTimePicker

then

Private Function GetNextInterval() As Long
        Dim DayToRun As Date = DayBox.Value
        Dim TargetDate As Date = New Date(DayToRun.Year, DayToRun.Month, DayToRun.Day, CInt(Split(TimeBox.Text, ":")(0)), CInt(Split(TimeBox.Text, ":")(1)), 0)

        Dim ts As TimeSpan
        If TargetDate > Now Then
            ts = TargetDate - Now
        Else
            ts = Now - TargetDate
        End If
        Return ts.TotalMilliseconds
 End Function

though changing my if/then statement to be more like jcoehoorn's would probably be better.

I thought I was going to be able to gloat and say my solution had less lines than Idle_Mind's ..... waaahh!

Thanks guys!

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Mike TomlinsonMiddle School Assistant TeacherCommented:
I wouldn't say you have a weird way of looking at things...  =)

Often times we already have one algorithm figured out in our heads...and this prevents us from seeing things from a different perspective.  That's one of the really nice things about EE...people read the problem and see completely different things...and then often bring different approaches to the table.

...don't start the "line counting" games though...we'll have to lump you in with the C/C++ programmers mentality of "less must be better!".   =\

Here is my algorithm with even fewer lines:
(it's super hard to read...but it ~must~ be better since it's shorter!)
    Private Function GetNextInterval() As Long
        Dim dtTarget As New DateTime(DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Year, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Month, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Day, CInt(Split(TimeBox.Text, ":")(0)), CInt(Split(TimeBox.Text, ":")(1)), 0)
        Return IIf(dtTarget < DateTime.Now, dtTarget.AddDays(7).Subtract(DateTime.Now).TotalMilliseconds, dtTarget.Subtract(DateTime.Now).TotalMilliseconds)
    End Function

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Mike TomlinsonMiddle School Assistant TeacherCommented:
For grits and shins...and the betterment of the world (NOT!)...   ;)

The long sought after "one liner" function:
    Private Function GetNextInterval() As Long
        Return IIf(New DateTime(DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Year, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Month, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Day, CInt(Split(TimeBox.Text, ":")(0)), CInt(Split(TimeBox.Text, ":")(1)), 0) < DateTime.Now, (New DateTime(DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Year, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Month, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Day, CInt(Split(TimeBox.Text, ":")(0)), CInt(Split(TimeBox.Text, ":")(1)), 0)).AddDays(7).Subtract(DateTime.Now).TotalMilliseconds, (New DateTime(DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Year, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Month, DateTime.Now.AddDays(DayBox.SelectedIndex - DateTime.Now.DayOfWeek).Day, CInt(Split(TimeBox.Text, ":")(0)), CInt(Split(TimeBox.Text, ":")(1)), 0)).Subtract(DateTime.Now).TotalMilliseconds)
    End Function

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sgaggerjAuthor Commented:
Yea, that's exactly why i post here too.

It's not that hard to read though, and it definitely IS better!!!!

/ducks for cover

=)

Thanks again!

J
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