How to use DATEADD function with variables?

Question

In classic ASP, I am unable to use DateAdd() with variables. I see no reason why this should work.

strTargetDate=DateAdd("d",visitDate,followDate)

visitDate is an incremental value -- 30, 60, 90, 180 etc. followDate is an actual date. However, I receive a type mismatch error using this code. Shouldn't this work??

@KenWhite VBScript is weakly typed (types are determined by assigned values) and does not obey type prefixes. Except for fixed arrays assignment never cause type errors. — Ekkehard.Horner
– Ekkehard.Horner, Commented Oct 23, 2013 at 14:53
When you say "unable", do you mean you are getting an error or an unexpected result? Edit your question to include the relevant information for either/both options. — AnonJr
– AnonJr, Commented Oct 23, 2013 at 14:54
@Ekkehard.Horner: Who said anything about 'type prefixes'? Variable names are a convenience to the programmer; I'm not aware of any language that actually uses type prefixes ("Hungarian notation") to determine variable types. — Ken White
– Ken White, Commented Oct 23, 2013 at 15:23
AtEveryBodyExceptKenWhite - don't try to make sense of KenWhite's and my comments (or my reference to his speculations in my answer), because he choose to delete his contributions I was refering to. — Ekkehard.Horner
– Ekkehard.Horner, Commented Oct 23, 2013 at 15:38

Ekkehard.Horner · Accepted Answer · 2013-10-23 17:52:03Z

2

Either visitDate isn't/can't be converted to a number, or followDate isn't/can't be converted to a date. So check the TypeName() of your input and pay attention to date formats.

Partly to show facts against @Ken's speculations:

>> s = "string"
>> WScript.Echo 0, s, TypeName(s)
>> s = DateAdd("d", 1, Now)
>> WScript.Echo 1, s, TypeName(s)
>> s = DateAdd("d", "1", CStr(now))
>> WScript.Echo 2, s, TypeName(s)
>> s = DateAdd("d", 1, "20/10/2013")
>>
0 string String
1 24.10.2013 17:05:54 Date
2 24.10.2013 17:05:54 Date
>> s = DateAdd("d", 1, "32.13.1")
>>
Error Number:       13
Error Description:  Type mismatch

Update wrt comment:

As computations involving Null should propagate Null, this

>> WScript.Echo TypeName(DateAdd("d", 1, Null))
>>
Null
>>

is no surprise. While you should handle Nulls for your DateAdd() in a way appropriate to your application, they are not the cause for the type mismatch.

Empty strings (""), however, could well be the culprits:

>> WScript.Echo TypeName(DateAdd("d", 1, ""))
>>
Error Number:       13
Error Description:  Type mismatch
>>

edited Oct 23, 2013 at 17:52

answered Oct 23, 2013 at 14:58

Ekkehard.Horner

38.8k2 gold badges50 silver badges101 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Steve Weaver Over a year ago

Im receiving a type mismatch on followDate. Would null DB entries in the table cause that?

Ansgar Wiechers Over a year ago

@SteveWeaver Please follow the advice you were given: check the TypeName of your two input values.

Steve Weaver Over a year ago

Both return as a string type. I just checked both. Will DateAdd not accept two string inputs? Also both variables return values. followDate returns the number 60, visitDate is returning a valid date.

Ansgar Wiechers Over a year ago

@SteveWeaver Then your arguments are in the wrong order. Since you're calling DateAdd("d", visitDate, followDate), visitDate should have the value 60, and followDate should have the date string.

Steve Weaver Over a year ago

Man I really hope thats not what I did. Ill check again as soon as I get to work in the morning and let you know.

|

Collectives™ on Stack Overflow

How to use DATEADD function with variables?

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related