Date math

rfresh · May 19, 2012

I was looking at the Users Guide but still can't figure out how to parse dates to get how many days. I want to set a date (Long) when my app first installs then check this date against today's date to determine if the trial period has expired. I want a 30 day trial period.

Do I use the

B4X:

DateTime.Add(DateTime.Now, 0, 0, 1)

method?

Thanks...

Jost aus Soest · May 19, 2012

All dates and timestamps in B4A are internally stored in Ticks, i. e. a long number representing the time/date in milliseconds. So you can use dates/times like numbers and can calc differences using simply math.

Example:

B4X:

DateNow = ...
DateInstalled = ...
NumberOfDays = (DateNow - DateInstalled) / 86400000
If NumberOfDays > 30 Then
  'Trial period expired...
Else
  'Valid trial period...
End If

(BTW: A day has 86400 seconds...)

klaus · May 19, 2012

You can also do it so:

B4X:

DateNow = ...
DateInstalled = ...
NumberOfDays = (DateNow - DateInstalled) / DateTime.TicksPerDay
If NumberOfDays > 30 Then
  'Trial period expired...
Else
  'Valid trial period...
End If

Best regards.

nfordbscndrd · May 19, 2012

rfresh said:
I was looking at the Users Guide but still can't figure out how to parse dates to get how many days. I want to set a date (Long) when my app first installs then check this date against today's date to determine if the trial period has expired. I want a 30 day trial period.

Do I use the

B4X:

DateTime.Add(DateTime.Now, 0, 0, 1)

method?

Thanks...

This is covered in the Documentation Wiki which also contains a link to a thread which gets into other considerations.

Mahares · May 19, 2012

If you want to use your datetime.add function, here is a method that yields the same result as Jost and Klaus, but with a different flavor:

B4X:

'BELOW To CALCULATE IF 30 DAY TRIAL PERIOD EXPIRED
Dim DateInstalled As String
DateInstalled = "4/20/2012"
If DateTime.Add(DateTime.dateparse(DateInstalled),0,0,30)< DateTime.Now Then
'Trial period expired...
   Msgbox("Expired","")
Else
  'Valid trial period...
   Msgbox("Not Expired","")
End If

Jost aus Soest · May 20, 2012

klaus said:
DateTime.TicksPerDay

Hehehe, notice to myself:
I must study all the members of an library!

Date math

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Date math

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