Dates and Time

1
Dates and Time

• We shall look at
• Getting the current system date.
• Getting the current system time.
• Comparing dates.
• Comparing times.

2
Getting the current system date.

• The simplest way of obtaining the current system
  date is to use the DateString function.
• The DateString function returns the date of the
  computer as set in the system's control panel.
• So for example
• txtTheDate.Text DateString

3
Getting the current system time.

• The simplest way of obtaining the current system
  time is to use the TimeString function.
• The TimeString function returns the time of the
  computer as set in the system's control panel.
• So for example
• txtTheTime.Text TimeString
• Would display the current time in a text box
  called txtTheTime.

4
The Date Data Type.

• The Date data type is what we use when we want to
  store either date or time values (there is no
  explicit Time Data Type in VB!)
• To declare a variable as Date you would do the
  following...
• Dim MyDateVar as Date

5
Comparing dates.

• Date comparisons may be performed much like any
  other data type, the following code is an
  example...
• Dim Date1 As Date
• Dim Date2 As Date
• Date1 1/2/66
• Date2 3/2/55
• If Date1 Date2 Then
• MessageBox.Show("The dates are the
  same.")
• End If

6
Now

• One function provided by VB is the function Now.
• The problem with DateString (and TimeString), as
  the name suggest, is that they return a data type
  of String.
• This creates a problem when performing date
  comparisons as comparing a String with a Date
  could potentially result in a crash.
• Now returns a value of Date data type but with
  one small problem!
• The value of Now incorporates both the Date and
  the Time!
• So the following is a valid example of data
  returned by Now...
• 31/1/2005 111923

7
Problem

• The problem with this is that it makes a
  comparison with a simple date value a little more
  tricky as we cant simply, for example, compare a
  date, e.g.
• 31/1/2005
• with the value returned by Now.
• 31/1/2005 111923

8
The Date Property

• For example the following code...
• Dim MyDate as Date
• MyDate Now
• MessageBox.Show(MyDate.Date)
• Would display...
• 31/1/2005
• Even though the actual value of MyDate is...
• 31/1/2005 111923

9
Comparing Times.

• Comparing times has some of the same problems as
  comparing dates but with a few extra
  complications.
• Simple time comparisons are not a problem as
  follows...
• Dim Time1 As Date
• Dim Time2 As Date
• Time1 1115
• Time2 1214
• If Time1 Time2 Then
• MessageBox.Show("The times are the
  same.")
• End If

10
Comparing Times.

• To compare a time value with Now, we need to
  compare the hours first, then compare the
  minutes, like so...
• Dim MyTime as Date
• MyTime 1137
• If MyTime.Hour Now.Hour Then
• If MyTime.Minute Now.Minute Then
• Messagebox.Show("Times are the same")
• End If
• End If