VBA Date Time Manipulation Conversion and Creation
Example
CDate()
CDate() converts something from any datatype to a Date datatype
Sub CDateExamples()
Dim sample As Date
' Converts a String representing a date and time to a Date
sample = CDate("September 11, 2001 12:34")
Debug.Print Format$(sample, "yyyy-mm-dd hh:nn:ss") ' prints 2001-09-11 12:34:00
' Converts a String containing a date to a Date
sample = CDate("September 11, 2001")
Debug.Print Format$(sample, "yyyy-mm-dd hh:nn:ss") ' prints 2001-09-11 00:00:00
' Converts a String containing a time to a Date
sample = CDate("12:34:56")
Debug.Print Hour(sample) ' prints 12
Debug.Print Minute(sample) ' prints 34
Debug.Print Second(sample) ' prints 56
' Find the 10000th day from the epoch date of 1899-12-31
sample = CDate(10000)
Debug.Print Format$(sample, "yyyy-mm-dd") ' prints 1927-05-18
End Sub
Note that VBA also has a loosely typed CVDate() that functions in the same way as the CDate() function other than returning a date typed Variant instead of a strongly typed Date. The CDate() version should be preferred when passing to a Date parameter or assigning to a Date variable, and the CVDate() version should be preferred when when passing to a Variant parameter or assigning to a Variant variable. This avoids implicit type casting.
DateSerial()
DateSerial() function is used to create a date. It returns a Date for a specified year, month, and day.
Syntax:
DateSerial ( year, month, day )
With year, month and day arguments being valid Integers (Year from 100 to 9999, Month from 1 to 12, Day from 1 to 31).
Examples
Sub DateSerialExamples()
' Build a specific date
Dim sample As Date
sample = DateSerial(2001, 9, 11)
Debug.Print Format$(sample, "yyyy-mm-dd") ' prints 2001-09-11
' Find the first day of the month for a date.
sample = DateSerial(Year(sample), Month(sample), 1)
Debug.Print Format$(sample, "yyyy-mm-dd") ' prints 2001-09-11
' Find the last day of the previous month.
sample = DateSerial(Year(sample), Month(sample), 1) - 1
Debug.Print Format$(sample, "yyyy-mm-dd") ' prints 2001-09-11
End Sub
Note that DateSerial() will accept "invalid" dates and calculate a valid date from it. This can be used creatively for good:
Positive Example
Sub GoodDateSerialExample()
'Calculate 45 days from today
Dim today As Date
today = DateSerial (2001, 9, 11)
Dim futureDate As Date
futureDate = DateSerial(Year(today), Month(today), Day(today) + 45)
Debug.Print Format$(futureDate, "yyyy-mm-dd") 'prints 2009-10-26
End Sub
However, it is more likely to cause grief when attempting to create a date from unvalidated user input:
Negative Example
Sub BadDateSerialExample()
'Allow user to enter unvalidate date information
Dim myYear As Long
myYear = InputBox("Enter Year")
'Assume user enters 2009
Dim myMonth As Long
myMonth = InputBox("Enter Month")
'Assume user enters 2
Dim myDay As Long
myDay = InputBox("Enter Day")
'Assume user enters 31
Debug.Print Format$(DateSerial(myYear, myMonth, myDay), "yyyy-mm-dd")
'prints 2009-03-03
End Sub
