Creating Random Dates in ColdFusion: RandDateRange( dtFrom, dtTo )
Posted July 7, 2006 at 3:08 PM
Someone was just asking me how to create a random date in ColdFusion. More specifically, how to create a random date between two dates. The solutions for this is quite simple once you understand it. I have created a method named RandDateRange(). This method functions similar to RandRange( intFrom, intTo ) and actually uses that method under the hood. If you abstract generating a random date between two given dates, it comes down to picking a random point in time. We can create this random point by adding a random time span to the "From Date", making sure, of course, that this random time span does not give us a date past the desired "To Date".
The beauty of time spans in ColdFusion is that they can be represented as a single floating point number. This puts us in the perfect position to use RandRange() to create random time spans. To make sure that we do not create too large a timespan, our bottom range parameter will be zero and our top range parameter will be the difference in seconds between the two out lier dates. Therefore, if we get a random second value and add it to the "From Date", we know we can never go past the "To Date."
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- <cffunction name="RandDateRange" access="public" returntype="date" output="false"
- hint="This returns a random date between the two given dates (inclusive).">
- <!--- Define arguments. --->
- <cfargument name="FromDate" type="date" required="true" />
- <cfargument name="ToDate" type="date" required="true" />
- <cfscript>
- // Define the local scope.
- var LOCAL = StructNew();
- // Get the difference in seconds between the two dates.
- LOCAL.TimeDifference = DateDiff(
- "s",
- ARGUMENTS.FromDate,
- ARGUMENTS.ToDate
- );
- // Create a random time increment based on the second difference.
- // The time span object is a representation of time-length in
- // terms of a single floating-point number.
- LOCAL.TimeIncrement = CreateTimeSpan(
- 0, // Days
- 0, // Hours
- 0, // Minutes
- RandRange( // Seconds
- // Our smallest possible time increment.
- 0,
- // Our largest possible time increment that will not
- // put us past the ToDate.
- LOCAL.TimeDifference
- )
- );
- // Get a new random date based on the FromDate and the random
- // time span.
- LOCAL.RandomDate = (ARGUMENTS.FromDate + LOCAL.TimeIncrement);
- // This random date now is formatted like a TimeSpan object,
- // meaning that it is in the form of one floating point number.
- return( LOCAL.RandomDate );
- </cfscript>
- </cffunction>
Now to test it out. For the from and to dates, let's pick Now and one month from Now.
From: 2006-07-07
To: 2006-08-07
Now, get a random date between those to:
Random: 38931.4080093
As you can see above, the random date is in Time Span format (represented as a single floating point number). In order to fix that, all we have to do is run a date format on it. Now, keep in mind that ColdFusion still treats that as a valid date. You only need to change the formatting on it for display. You can add, diff, subtract all you want on the server side and its all good.
Formatted: 2006-08-02
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