Page History: IsDate and IsTime functions (VB Work-A-Like)
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Page Revision: 2018/09/11 08:49
The following are two functions to validate dates and times.
Inspired by the VB functions of the same name.
Often when a user is asked to enter either, there is quite a bit of code to make sure that what they entered makes sense. These functions provide a compact check on both the format and values and return a boolean (actually an integer) of 0 if the string is not a Date/Time. Non zero indicates the string is valid.
Notes IsDate:- Supports both UK/AUS time formats of dd/mm/yyyy or international sort format of yyyy/mm/dd
- If opt is zero or absent for IsDate, system default format is assumed, if opt is non-zero, international format is assumed.
- The delimiter may be either / or - e.g. dd-mm-yyyy or dd/mm/yyyy is fine.
Notes IsTime:- Times must be formatted as hh:mm (no seconds allowed but you could easily tweak it)
Syntax:=IsTime(TimeStr$)
=IsDate(DateStr$,[opt])
Examples:If Not IsDate(dt$,1) then exit Sub
Checkbox=Istime(A$)
Dependencies:IsLeapYear FunctionRegular Expression Function
Function IsTime(t$) As Integer
IsTime=0
If Match("^[012][0123456789]:[012345][0123456789]$",t$) Then
If Val(Left$(t$,2))<24 Then
If Val(Right$(t$,2))<60 Then
IsTime=1
EndIf
EndIf
EndIf
End Function
Function IsDate(t$,opt As Integer) As Integer
Local Integer d,m,y
IsDate=0
If opt=0 then
If Match("^[0123][0123456789][/|-][01][0123456789][/|-][12][0123456789][0123456789][0123456789]$",t$)=0 Then Exit Function
d=Val(Left$(t$,2))
m=Val(Mid$(t$,4,2))
y=Val(Right$(t$,4))
Else
If Match("^[12][0123456789][0123456789][0123456789][/|-][01][0123456789][/|-][0123][0123456789]$",t$)=0 Then Exit Function
d=Val(Right$(t$,2))
m=Val(Mid$(t$,6,2))
y=Val(Left$(t$,4))
EndIf
Select Case m
Case 1,3,5,7,8,10,12
if d<1 or d>31 Then Exit Function
Case 4,6,9,11
if d<1 or d>30 Then Exit Function
Case 2
if d<1 or d>28+IsLeapYear(y) Then Exit Function
End Select
IsDate=1
End Function